diff --git a/src/main/java/cnu/mvc/domain/member/MemberRepository.java b/src/main/java/cnu/mvc/domain/member/MemberRepository.java
index 1b273fc..e2a45c5 100644
--- a/src/main/java/cnu/mvc/domain/member/MemberRepository.java
+++ b/src/main/java/cnu/mvc/domain/member/MemberRepository.java
@@ -22,7 +22,10 @@ public Member findById(Long id) {
 
     // 구현
     public Member findByEmail(String email) {
-        return null;
+        return store.values().stream()
+                .filter(member -> member.getEmail().equals(email))
+                .findFirst()
+                .orElse(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..8d494a8 100644
--- a/src/main/java/cnu/mvc/domain/member/MemberService.java
+++ b/src/main/java/cnu/mvc/domain/member/MemberService.java
@@ -10,11 +10,19 @@ public class MemberService {
     private final MemberRepository memberRepository;
 
     public Member join(Member member){
+        // 이메일 중복 검사
+        Member findMember = findByEmail(member.getEmail());
+        if (findMember != null) {
+            throw new IllegalStateException("이미 존재하는 이메일 계정입니다.");
+        }
         return memberRepository.save(member);
     }
 
     public Member validateMember(String email, String pwd) {
-        Member findMember = findById(1L);
+        Member findMember = findByEmail(email);
+        if (findMember == null || !findMember.getPwd().equals(pwd)) {
+            throw new IllegalStateException("이메일 또는 비밀번호를 확인해주세요.");
+        }
         return findMember;
     }