diff --git a/src/main/java/backend/likelion/todos/goal/Goal.java b/src/main/java/backend/likelion/todos/goal/Goal.java
index 178d14d..1f05f49 100644
--- a/src/main/java/backend/likelion/todos/goal/Goal.java
+++ b/src/main/java/backend/likelion/todos/goal/Goal.java
@@ -2,20 +2,30 @@
 
 import backend.likelion.todos.common.ForbiddenException;
 import backend.likelion.todos.member.Member;
+import jakarta.persistence.*;
+import lombok.AccessLevel;
 import lombok.Getter;
+import lombok.NoArgsConstructor;
 
 
 @Getter
 // TODO [10 단계] : 롬봉을 통해 기본 생성자를 PROTECTED 접근 제한자로 생성하세요.
+@NoArgsConstructor(access = AccessLevel.PROTECTED)
+
 // TODO [10 단계] : Goal 객체를 Entity 로 정의하세요.
+@Entity
 public class Goal {
 
     // TODO [10 단계] : id를 PK, Auto Increment로 설정하세요.
+    @Id
+    @GeneratedValue(strategy = GenerationType.AUTO)
     private Long id;
     private String name;
     private String color;
 
     // TODO [10 단계] : goal 과 member와의 관계를 설정합니다. (join 하는 컬럼명은 member_id로 설정합니다.), 지연 로딩을 사용합니다.
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn(name = "member_id")
     private Member member;
 
     public Goal(String name, String color, Member member) {
diff --git a/src/main/java/backend/likelion/todos/goal/GoalRepository.java b/src/main/java/backend/likelion/todos/goal/GoalRepository.java
index 9d9ae11..dd26340 100644
--- a/src/main/java/backend/likelion/todos/goal/GoalRepository.java
+++ b/src/main/java/backend/likelion/todos/goal/GoalRepository.java
@@ -1,17 +1,14 @@
 package backend.likelion.todos.goal;
 
 import java.util.List;
+
+import org.springframework.data.jpa.repository.JpaRepository;
 import org.springframework.stereotype.Repository;
 
 @Repository
-public interface GoalRepository {
+public interface GoalRepository extends JpaRepository<Goal, Long> {
     // TODO [10단계] JpaRepository를 상속받습니다.
 
     // TODO [10단계] 아래는 기존 코드입니다. 컴파일 오류가 발생하고 있는데, 이를 해결하세요.
-    public List<Goal> findAllByMemberId(Long memberId) {
-        return goals.values()
-                .stream()
-                .filter(it -> it.getMember().getId().equals(memberId))
-                .toList();
-    }
+    List<Goal> findAllByMemberId(Long memberId);
 }
diff --git a/src/main/java/backend/likelion/todos/member/Member.java b/src/main/java/backend/likelion/todos/member/Member.java
index 1b7ca66..eb8612d 100644
--- a/src/main/java/backend/likelion/todos/member/Member.java
+++ b/src/main/java/backend/likelion/todos/member/Member.java
@@ -1,17 +1,25 @@
 package backend.likelion.todos.member;
 
 import backend.likelion.todos.common.UnAuthorizedException;
+import jakarta.persistence.*;
+import lombok.AccessLevel;
 import lombok.Getter;
+import lombok.NoArgsConstructor;
 
 @Getter
 // TODO [10 단계] : 롬봉을 통해 기본 생성자를 PROTECTED 접근 제한자로 생성하세요.
 // TODO [10 단계] : Member 객체를 Entity 로 정의하세요.
+@Entity
+@NoArgsConstructor(access = AccessLevel.PROTECTED)
 public class Member {
 
     // TODO [10 단계] : id를 PK, Auto Increment로 설정하세요.
+    @Id
+    @GeneratedValue(strategy = GenerationType.AUTO)
     private Long id;
 
     // TODO [10 단계] : 아이디는 unique 제약 조건이 필요합니다.
+    @Column(unique = true)
     private String username;
 
     private String password;
diff --git a/src/main/java/backend/likelion/todos/member/MemberRepository.java b/src/main/java/backend/likelion/todos/member/MemberRepository.java
index fc49807..ab6524b 100644
--- a/src/main/java/backend/likelion/todos/member/MemberRepository.java
+++ b/src/main/java/backend/likelion/todos/member/MemberRepository.java
@@ -1,17 +1,14 @@
 package backend.likelion.todos.member;
 
 import java.util.Optional;
+
+import org.springframework.data.jpa.repository.JpaRepository;
 import org.springframework.stereotype.Repository;
 
 @Repository
-public interface MemberRepository {
+public interface MemberRepository extends JpaRepository<Member, Long> {
     // TODO [10단계] JpaRepository를 상속받습니다.
 
     // TODO [10단계] 아래는 기존 코드입니다. 컴파일 오류가 발생하고 있는데, 이를 해결하세요.
-    public Optional<Member> findByUsername(String username) {
-        return members.values()
-                .stream()
-                .filter(it -> it.getUsername().equals(username))
-                .findAny();
-    }
+    Optional<Member> findByUserName(String username);
 }
diff --git a/src/main/java/backend/likelion/todos/todo/Todo.java b/src/main/java/backend/likelion/todos/todo/Todo.java
index 672f39e..79e2130 100644
--- a/src/main/java/backend/likelion/todos/todo/Todo.java
+++ b/src/main/java/backend/likelion/todos/todo/Todo.java
@@ -3,22 +3,32 @@
 import backend.likelion.todos.common.ForbiddenException;
 import backend.likelion.todos.goal.Goal;
 import backend.likelion.todos.member.Member;
-import jakarta.persistence.Entity;
+import jakarta.persistence.*;
+
 import java.time.LocalDate;
+
+import lombok.AccessLevel;
 import lombok.Getter;
+import lombok.NoArgsConstructor;
 
 @Getter
 // TODO [10 단계] : 롬봉을 통해 기본 생성자를 PROTECTED 접근 제한자로 생성하세요.
 // TODO [10 단계] : Todo 객체를 Entity 로 정의하세요.
+@Entity
+@NoArgsConstructor(access = AccessLevel.PROTECTED)
 public class Todo {
 
     // TODO [10 단계] : id를 PK, Auto Increment로 설정하세요.
+    @Id
+    @GeneratedValue(strategy = GenerationType.AUTO)
     private Long id;
 
     private String content;
     private LocalDate date;
 
     // TODO [10 단계] : todo 와 goal 과의 관계를 설정합니다. (join 하는 컬럼명은 goal_id로 설정합니다.), 지연 로딩을 사용합니다.
+    @ManyToOne(fetch = FetchType.LAZY)
+    @JoinColumn(name = "goal_id")
     private Goal goal;
     private boolean isCompleted;
 
diff --git a/src/main/java/backend/likelion/todos/todo/TodoRepository.java b/src/main/java/backend/likelion/todos/todo/TodoRepository.java
index 7609d41..cd25ad0 100644
--- a/src/main/java/backend/likelion/todos/todo/TodoRepository.java
+++ b/src/main/java/backend/likelion/todos/todo/TodoRepository.java
@@ -7,7 +7,7 @@
 import org.springframework.stereotype.Repository;
 
 @Repository
-public interface TodoRepository {
+public interface TodoRepository extends JpaRepository<Todo, Long> {
     // TODO [10단계] JpaRepository를 상속받습니다.
 
     /**