diff --git a/.DS_Store b/.DS_Store
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index 0000000..fe38da8
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diff --git a/src/.DS_Store b/src/.DS_Store
new file mode 100644
index 0000000..69134ed
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diff --git a/src/main/.DS_Store b/src/main/.DS_Store
new file mode 100644
index 0000000..410c4fb
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diff --git a/src/main/java/.DS_Store b/src/main/java/.DS_Store
new file mode 100644
index 0000000..78fcc8c
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diff --git a/src/main/java/cnu/.DS_Store b/src/main/java/cnu/.DS_Store
new file mode 100644
index 0000000..dd890b0
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diff --git a/src/main/java/cnu/mvc/.DS_Store b/src/main/java/cnu/mvc/.DS_Store
new file mode 100644
index 0000000..29d62b6
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diff --git a/src/main/java/cnu/mvc/domain/.DS_Store b/src/main/java/cnu/mvc/domain/.DS_Store
new file mode 100644
index 0000000..201b8df
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diff --git a/src/main/java/cnu/mvc/domain/member/MemberRepository.java b/src/main/java/cnu/mvc/domain/member/MemberRepository.java
index 1b273fc..fdf1f70 100644
--- a/src/main/java/cnu/mvc/domain/member/MemberRepository.java
+++ b/src/main/java/cnu/mvc/domain/member/MemberRepository.java
@@ -21,8 +21,14 @@ public Member findById(Long id) {
     }
 
     // 구현
+    // 이메일이 일치하는 회원 반환
     public Member findByEmail(String email) {
-        return null;
+        for (Member member : store.values()) {
+            if (member.getEmail().equals(email)) {
+                return member; // 찾으면 반환
+            }
+        }
+        return null; // 없으면 null
     }
 }
 
diff --git a/src/main/java/cnu/mvc/domain/member/MemberService.java b/src/main/java/cnu/mvc/domain/member/MemberService.java
index b8e785e..6984ac8 100644
--- a/src/main/java/cnu/mvc/domain/member/MemberService.java
+++ b/src/main/java/cnu/mvc/domain/member/MemberService.java
@@ -9,12 +9,27 @@ public class MemberService {
 
     private final MemberRepository memberRepository;
 
-    public Member join(Member member){
+    // 회원 가입
+    public Member join(Member member) {
+        Member findMember = findByEmail(member.getEmail());
+        if (findMember != null) {
+            // 이미 등록된 이메일인 경우 예외 발생
+            throw new IllegalStateException("이미 존재하는 이메일 계정입니다.");
+        }
+        // 새 회원 저장
         return memberRepository.save(member);
     }
 
+    // 로그인 유효성 검사
     public Member validateMember(String email, String pwd) {
-        Member findMember = findById(1L);
+        Member findMember = findByEmail(email);
+
+        // 이메일이 없거나 비밀번호가 틀린 경우 예외 발생
+        if (findMember == null || !findMember.getPwd().equals(pwd)) {
+            throw new IllegalStateException("이메일 또는 비밀번호를 확인해주세요.");
+        }
+
+        // 로그인 성공
         return findMember;
     }