diff --git a/src/main/java/cnu/mvc/domain/member/MemberRepository.java b/src/main/java/cnu/mvc/domain/member/MemberRepository.java
index 1b273fc..6617dfc 100644
--- a/src/main/java/cnu/mvc/domain/member/MemberRepository.java
+++ b/src/main/java/cnu/mvc/domain/member/MemberRepository.java
@@ -22,7 +22,12 @@ public Member findById(Long id) {
 
     // 구현
     public Member findByEmail(String email) {
-        return null;
+    for (Member member : store.values()) {
+        if (member.getEmail().equals(email)) {
+            return member;
+        }
     }
+    return 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..4fca422 100644
--- a/src/main/java/cnu/mvc/domain/member/MemberService.java
+++ b/src/main/java/cnu/mvc/domain/member/MemberService.java
@@ -10,12 +10,21 @@ public class MemberService {
     private final MemberRepository memberRepository;
 
     public Member join(Member member){
+        if(memberRepository.findByEmail(member.getEmail()) != null) {
+            throw new IllegalStateException("이미 존재하는 이메일입니다.");
+        }
+
         return memberRepository.save(member);
     }
 
     public Member validateMember(String email, String pwd) {
-        Member findMember = findById(1L);
-        return findMember;
+        Member member = memberRepository.findByEmail(email);
+
+        if(member == null || !member.getPwd().equals(pwd)) {
+            throw new IllegalArgumentException("이메일 또는 비밀번호를 확인해주세요.");
+        }
+
+        return member;
     }
 
     public Member findById(Long id) {