diff --git a/.gitignore b/.gitignore
index c2065bc..9bd38c3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -35,3 +35,4 @@ out/
 
 ### VS Code ###
 .vscode/
+.env
\ No newline at end of file
diff --git a/build.gradle b/build.gradle
index 610d6a6..8f83701 100644
--- a/build.gradle
+++ b/build.gradle
@@ -19,9 +19,11 @@ repositories {
 }
 
 dependencies {
-	implementation 'org.springframework.boot:spring-boot-starter-web'
-	testImplementation 'org.springframework.boot:spring-boot-starter-test'
-	testRuntimeOnly 'org.junit.platform:junit-platform-launcher'
+    implementation 'org.springframework.boot:spring-boot-starter-web'
+    implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
+    runtimeOnly 'com.mysql:mysql-connector-j'
+    testImplementation 'org.springframework.boot:spring-boot-starter-test'
+    testRuntimeOnly 'org.junit.platform:junit-platform-launcher'
 }
 
 tasks.named('test') {
diff --git a/src/main/java/com/example/devSns/comment/Comment.java b/src/main/java/com/example/devSns/comment/Comment.java
new file mode 100644
index 0000000..39b1273
--- /dev/null
+++ b/src/main/java/com/example/devSns/comment/Comment.java
@@ -0,0 +1,37 @@
+package com.example.devSns.comment;
+
+import com.example.devSns.task.Task;
+import jakarta.persistence.*;
+import java.time.LocalDateTime;
+
+@Entity
+@Table(name = "comments")
+public class Comment {
+
+    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @Column(nullable = false, length = 1000)
+    private String content;
+
+    private String username;
+    private LocalDateTime createdAt = LocalDateTime.now();
+
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn(name = "task_id")
+    private Task task;
+
+    protected Comment() {}
+
+    public Comment(String content, String username, Task task) {
+        this.content = content;
+        this.username = username;
+        this.task = task;
+    }
+
+    public Long getId() { return id; }
+    public String getContent() { return content; }
+    public String getUsername() { return username; }
+    public LocalDateTime getCreatedAt() { return createdAt; }
+    public Task getTask() { return task; }
+}
diff --git a/src/main/java/com/example/devSns/comment/CommentController.java b/src/main/java/com/example/devSns/comment/CommentController.java
new file mode 100644
index 0000000..27c85a4
--- /dev/null
+++ b/src/main/java/com/example/devSns/comment/CommentController.java
@@ -0,0 +1,37 @@
+package com.example.devSns.comment;
+
+import com.example.devSns.comment.dto.CommentRequest;
+import com.example.devSns.comment.dto.CommentResponse;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
+import java.util.List;
+
+@RestController
+@RequestMapping("/api/tasks/{taskId}/comments")
+public class CommentController {
+    private final CommentService service;
+
+    public CommentController(CommentService service) {
+        this.service = service;
+    }
+
+    @PostMapping
+    public ResponseEntity<CommentResponse> create(
+            @PathVariable Long taskId,
+            @RequestBody CommentRequest req) {
+        return ResponseEntity.ok(service.create(taskId, req));
+    }
+
+    @GetMapping
+    public List<CommentResponse> list(@PathVariable Long taskId) {
+        return service.findByTask(taskId);
+    }
+
+    @DeleteMapping("/{commentId}")
+    public ResponseEntity<Void> delete(
+            @PathVariable Long taskId,
+            @PathVariable Long commentId) {
+        service.delete(commentId);
+        return ResponseEntity.noContent().build();
+    }
+}
diff --git a/src/main/java/com/example/devSns/comment/CommentRepository.java b/src/main/java/com/example/devSns/comment/CommentRepository.java
new file mode 100644
index 0000000..e32d79a
--- /dev/null
+++ b/src/main/java/com/example/devSns/comment/CommentRepository.java
@@ -0,0 +1,8 @@
+package com.example.devSns.comment;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+import java.util.List;
+
+public interface CommentRepository extends JpaRepository<Comment, Long> {
+    List<Comment> findByTaskId(Long taskId);
+}
diff --git a/src/main/java/com/example/devSns/comment/CommentService.java b/src/main/java/com/example/devSns/comment/CommentService.java
new file mode 100644
index 0000000..6179550
--- /dev/null
+++ b/src/main/java/com/example/devSns/comment/CommentService.java
@@ -0,0 +1,36 @@
+package com.example.devSns.comment;
+
+import com.example.devSns.comment.dto.CommentRequest;
+import com.example.devSns.comment.dto.CommentResponse;
+import com.example.devSns.task.Task;
+import com.example.devSns.task.TaskRepository;
+import org.springframework.stereotype.Service;
+import java.util.List;
+
+@Service
+public class CommentService {
+    private final CommentRepository commentRepo;
+    private final TaskRepository taskRepo;
+
+    public CommentService(CommentRepository commentRepo, TaskRepository taskRepo) {
+        this.commentRepo = commentRepo;
+        this.taskRepo = taskRepo;
+    }
+
+    public CommentResponse create(Long taskId, CommentRequest req) {
+        Task task = taskRepo.findById(taskId)
+                .orElseThrow(() -> new IllegalArgumentException("Task not found"));
+        Comment comment = new Comment(req.getContent(), req.getUsername(), task);
+        Comment saved = commentRepo.save(comment);
+        return new CommentResponse(saved);
+    }
+
+    public List<CommentResponse> findByTask(Long taskId) {
+        return commentRepo.findByTaskId(taskId)
+                .stream().map(CommentResponse::new).toList();
+    }
+
+    public void delete(Long commentId) {
+        commentRepo.deleteById(commentId);
+    }
+}
diff --git a/src/main/java/com/example/devSns/comment/dto/CommentRequest.java b/src/main/java/com/example/devSns/comment/dto/CommentRequest.java
new file mode 100644
index 0000000..dcddd5d
--- /dev/null
+++ b/src/main/java/com/example/devSns/comment/dto/CommentRequest.java
@@ -0,0 +1,24 @@
+package com.example.devSns.comment.dto;
+
+public class CommentRequest {
+    private String content;
+    private String username;
+
+    public CommentRequest() {}
+
+    public String getContent() {
+        return content;
+    }
+
+    public void setContent(String content) {   // ← 이거 추가
+        this.content = content;
+    }
+
+    public String getUsername() {
+        return username;
+    }
+
+    public void setUsername(String username) { // ← 이거 추가
+        this.username = username;
+    }
+}
diff --git a/src/main/java/com/example/devSns/comment/dto/CommentResponse.java b/src/main/java/com/example/devSns/comment/dto/CommentResponse.java
new file mode 100644
index 0000000..6e6eacb
--- /dev/null
+++ b/src/main/java/com/example/devSns/comment/dto/CommentResponse.java
@@ -0,0 +1,23 @@
+package com.example.devSns.comment.dto;
+
+import com.example.devSns.comment.Comment;
+import java.time.LocalDateTime;
+
+public class CommentResponse {
+    private Long id;
+    private String content;
+    private String username;
+    private LocalDateTime createdAt;
+
+    public CommentResponse(Comment comment) {
+        this.id = comment.getId();
+        this.content = comment.getContent();
+        this.username = comment.getUsername();
+        this.createdAt = comment.getCreatedAt();
+    }
+
+    public Long getId() { return id; }
+    public String getContent() { return content; }
+    public String getUsername() { return username; }
+    public LocalDateTime getCreatedAt() { return createdAt; }
+}
diff --git a/src/main/java/com/example/devSns/task/Task.java b/src/main/java/com/example/devSns/task/Task.java
new file mode 100644
index 0000000..73d05b9
--- /dev/null
+++ b/src/main/java/com/example/devSns/task/Task.java
@@ -0,0 +1,48 @@
+package com.example.devSns.task;
+
+import com.example.devSns.comment.Comment;
+import jakarta.persistence.*;
+import java.time.LocalDate;
+import java.util.ArrayList;
+import java.util.List;
+
+@Entity
+@Table(name = "tasks")
+public class Task {
+
+    public enum Status { TODO, IN_PROGRESS, DONE }
+
+    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @Column(nullable = false)
+    private String title;
+
+    @Column(length = 2000)
+    private String description;
+
+    private LocalDate dueDate;
+    private Integer priority;
+
+    @Enumerated(EnumType.STRING)
+    @Column(nullable = false)
+    private Status status = Status.TODO;
+
+    @OneToMany(mappedBy = "task", cascade = CascadeType.ALL, orphanRemoval = true)
+    private List<Comment> comments = new ArrayList<>();
+
+    protected Task() {}
+
+    public Long getId() { return id; }
+    public String getTitle() { return title; }
+    public void setTitle(String title) { this.title = title; }
+    public String getDescription() { return description; }
+    public void setDescription(String description) { this.description = description; }
+    public LocalDate getDueDate() { return dueDate; }
+    public void setDueDate(LocalDate dueDate) { this.dueDate = dueDate; }
+    public Integer getPriority() { return priority; }
+    public void setPriority(Integer priority) { this.priority = priority; }
+    public Status getStatus() { return status; }
+    public void setStatus(Status status) { this.status = status; }
+    public List<Comment> getComments() { return comments; }
+}
diff --git a/src/main/java/com/example/devSns/task/TaskController.java b/src/main/java/com/example/devSns/task/TaskController.java
new file mode 100644
index 0000000..1b834ef
--- /dev/null
+++ b/src/main/java/com/example/devSns/task/TaskController.java
@@ -0,0 +1,53 @@
+package com.example.devSns.task;
+
+import com.example.devSns.task.dto.TaskRequest;
+import com.example.devSns.task.dto.TaskResponse;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
+
+import java.net.URI;
+import java.util.List;
+
+@RestController
+@RequestMapping("/api/tasks")
+public class TaskController {
+
+    private final TaskService service;
+
+    public TaskController(TaskService service) {
+        this.service = service;
+    }
+
+    @PostMapping
+    public ResponseEntity<TaskResponse> create(@RequestBody TaskRequest req) {
+        Task saved = service.create(req);
+        return ResponseEntity.created(URI.create("/api/tasks/" + saved.getId()))
+                .body(new TaskResponse(saved));
+    }
+
+    @GetMapping
+    public ResponseEntity<List<TaskResponse>> list() {
+        List<TaskResponse> tasks = service.findAll().stream()
+                .map(TaskResponse::new)
+                .toList();
+        return ResponseEntity.ok(tasks);
+    }
+
+    @GetMapping("/{id}")
+    public ResponseEntity<TaskResponse> get(@PathVariable Long id) {
+        Task found = service.findById(id);
+        return ResponseEntity.ok(new TaskResponse(found));
+    }
+
+    @PutMapping("/{id}")
+    public ResponseEntity<TaskResponse> update(@PathVariable Long id, @RequestBody TaskRequest req) {
+        Task updated = service.update(id, req);
+        return ResponseEntity.ok(new TaskResponse(updated));
+    }
+
+    @DeleteMapping("/{id}")
+    public ResponseEntity<Void> delete(@PathVariable Long id) {
+        service.delete(id);
+        return ResponseEntity.noContent().build();
+    }
+}
diff --git a/src/main/java/com/example/devSns/task/TaskNotFound.java b/src/main/java/com/example/devSns/task/TaskNotFound.java
new file mode 100644
index 0000000..7066533
--- /dev/null
+++ b/src/main/java/com/example/devSns/task/TaskNotFound.java
@@ -0,0 +1,5 @@
+package com.example.devSns.task;
+
+public class TaskNotFound extends RuntimeException {
+    public TaskNotFound(Long id) { super("Task not found: " + id); }
+}
diff --git a/src/main/java/com/example/devSns/task/TaskRepository.java b/src/main/java/com/example/devSns/task/TaskRepository.java
new file mode 100644
index 0000000..3e9aa55
--- /dev/null
+++ b/src/main/java/com/example/devSns/task/TaskRepository.java
@@ -0,0 +1,7 @@
+//DB에 저장·조회·삭제 등을 대신 처리
+
+package com.example.devSns.task;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+
+public interface TaskRepository extends JpaRepository<Task, Long> { }
\ No newline at end of file
diff --git a/src/main/java/com/example/devSns/task/TaskService.java b/src/main/java/com/example/devSns/task/TaskService.java
new file mode 100644
index 0000000..0362a94
--- /dev/null
+++ b/src/main/java/com/example/devSns/task/TaskService.java
@@ -0,0 +1,46 @@
+//컨트롤러와 DB 사이의 중간 관리자
+
+package com.example.devSns.task;
+
+import com.example.devSns.task.dto.TaskRequest;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+import java.util.List;
+
+@Service
+@Transactional
+public class TaskService {
+    private final TaskRepository repo;
+    public TaskService(TaskRepository repo) { this.repo = repo; }
+
+    public Task create(TaskRequest r) {
+        Task t = new Task();
+        if (r.title != null) t.setTitle(r.title);
+        t.setDescription(r.description);
+        t.setDueDate(r.dueDate);
+        t.setPriority(r.priority);
+        t.setStatus(r.status == null ? Task.Status.TODO : r.status);
+        return repo.save(t);
+    }
+
+    @Transactional(readOnly = true)
+    public List<Task> findAll() { return repo.findAll(); }
+
+    @Transactional(readOnly = true)
+    public Task findById(Long id) { // 값이 없으면 TaskNotFound
+        return repo.findById(id).orElseThrow(() -> new TaskNotFound(id));
+    }
+
+    public Task update(Long id, TaskRequest r) { //부분 수정 가능
+        Task t = findById(id);
+        if (r.title != null) t.setTitle(r.title);
+        if (r.description != null) t.setDescription(r.description);
+        if (r.dueDate != null) t.setDueDate(r.dueDate);
+        if (r.priority != null) t.setPriority(r.priority);
+        if (r.status != null) t.setStatus(r.status);
+        return t; // JPA dirty checking
+    }
+
+    public void delete(Long id) { repo.delete(findById(id));  }
+} // 존재하지 않으면 TaskNotFound
diff --git a/src/main/java/com/example/devSns/task/dto/TaskRequest.java b/src/main/java/com/example/devSns/task/dto/TaskRequest.java
new file mode 100644
index 0000000..d43ba4c
--- /dev/null
+++ b/src/main/java/com/example/devSns/task/dto/TaskRequest.java
@@ -0,0 +1,14 @@
+//client가 보낸 json 요청 받기 위한 dto
+
+package com.example.devSns.task.dto;
+
+import com.example.devSns.task.Task;
+import java.time.LocalDate;
+
+public class TaskRequest {
+    public String title;
+    public String description;
+    public LocalDate dueDate;
+    public Integer priority;
+    public Task.Status status;
+}
diff --git a/src/main/java/com/example/devSns/task/dto/TaskResponse.java b/src/main/java/com/example/devSns/task/dto/TaskResponse.java
new file mode 100644
index 0000000..23d5549
--- /dev/null
+++ b/src/main/java/com/example/devSns/task/dto/TaskResponse.java
@@ -0,0 +1,24 @@
+//DB에서 가져온 엔티티를 clinet에게 보낼 형식으로 만드는 DTO
+
+package com.example.devSns.task.dto;
+
+import com.example.devSns.task.Task;
+import java.time.LocalDate;
+
+public class TaskResponse {
+    public Long id;
+    public String title;
+    public String description;
+    public LocalDate dueDate;
+    public Integer priority;
+    public Task.Status status;
+
+    public TaskResponse(Task t) {
+        this.id = t.getId();
+        this.title = t.getTitle();
+        this.description = t.getDescription();
+        this.dueDate = t.getDueDate();
+        this.priority = t.getPriority();
+        this.status = t.getStatus();
+    }
+}
diff --git a/src/main/resources/application.properties b/src/main/resources/application.properties
index f3f10af..499d539 100644
--- a/src/main/resources/application.properties
+++ b/src/main/resources/application.properties
@@ -1 +1,13 @@
 spring.application.name=devSns
+
+# DB ???? (?????? ??)
+spring.datasource.url=${DATASOURCE_URL}
+spring.datasource.username=${DATASOURCE_USERNAME}
+spring.datasource.password=${DATASOURCE_PASSWORD}
+spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
+spring.datasource.hikari.connection-timeout=5000
+
+# JPA ??
+spring.jpa.hibernate.ddl-auto=update
+spring.jpa.show-sql=true
+spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL8Dialect
\ No newline at end of file