diff --git a/app/src/main/java/com/example/sprout/refactor/notification/Observable.java b/app/src/main/java/com/example/sprout/refactor/notification/Observable.java
new file mode 100644
index 0000000..3fc1923
--- /dev/null
+++ b/app/src/main/java/com/example/sprout/refactor/notification/Observable.java
@@ -0,0 +1,35 @@
+package com.example.sprout.refactor.notification;
+
+import java.util.ArrayList;
+
+/**
+ * Observable
+ *
+ * @param <T> 監視したいObject
+ * @author matsumoto_k
+ */
+
+public class Observable<T> {
+
+    private ArrayList<Observer<T>> observers = new ArrayList<>();
+
+    public void notifyObservers(T t) {
+        for (Observer<T> observer : observers) {
+            observer.notify(t);
+        }
+    }
+
+    public void notifyError(Throwable throwable) {
+        for (Observer<T> observer : observers) {
+            observer.error(throwable);
+        }
+    }
+
+    public void addObserver(Observer<T> observer) {
+        observers.add(observer);
+    }
+
+    public void removeObserver(Observer<T> observer) {
+        observers.remove(observer);
+    }
+}
diff --git a/app/src/main/java/com/example/sprout/refactor/notification/Observer.java b/app/src/main/java/com/example/sprout/refactor/notification/Observer.java
new file mode 100644
index 0000000..a2ee92d
--- /dev/null
+++ b/app/src/main/java/com/example/sprout/refactor/notification/Observer.java
@@ -0,0 +1,13 @@
+package com.example.sprout.refactor.notification;
+
+/**
+ * Observer
+ *
+ * @param <T> 監視させるObject
+ * @author matsumoto_k
+ */
+public abstract class Observer<T> {
+    public abstract void notify(T t);
+
+    public abstract void error(Throwable throwable);
+}
diff --git a/app/src/main/java/com/example/sprout/refactor/repository/RegistrationRepository.java b/app/src/main/java/com/example/sprout/refactor/repository/RegistrationRepository.java
index 5d79da2..658cdc9 100644
--- a/app/src/main/java/com/example/sprout/refactor/repository/RegistrationRepository.java
+++ b/app/src/main/java/com/example/sprout/refactor/repository/RegistrationRepository.java
@@ -1,6 +1,7 @@
 package com.example.sprout.refactor.repository;
 
 import com.example.sprout.refactor.api.SproutService;
+import com.example.sprout.refactor.notification.Observable;
 import com.example.sprout.refactor.vo.Account;
 
 import retrofit2.Call;
@@ -15,23 +16,28 @@
 public class RegistrationRepository extends Repository {
 
     private SproutService sproutService = null;
+    private Observable<Account> accountObservable = new Observable<>();
 
     public RegistrationRepository(SproutService sproutService) {
         this.sproutService = sproutService;
     }
 
-    public void registration(String userName, final Listener<Account> listener) {
+    public void registration(String userName) {
         Call<Account> task = sproutService.registration(userName);
         task.enqueue(new Callback<Account>() {
             @Override
             public void onResponse(Call<Account> call, Response<Account> response) {
-                listener.onSuccess(response.body());
+                accountObservable.notifyObservers(response.body());
             }
 
             @Override
             public void onFailure(Call<Account> call, Throwable t) {
-                listener.onFailure(t);
+                accountObservable.notifyError(t);
             }
         });
     }
+
+    public Observable<Account> getAccountObservable() {
+        return accountObservable;
+    }
 }
\ No newline at end of file
diff --git a/app/src/main/java/com/example/sprout/refactor/viewmodel/RegistrationViewModel.java b/app/src/main/java/com/example/sprout/refactor/viewmodel/RegistrationViewModel.java
index b81eeed..2c92402 100644
--- a/app/src/main/java/com/example/sprout/refactor/viewmodel/RegistrationViewModel.java
+++ b/app/src/main/java/com/example/sprout/refactor/viewmodel/RegistrationViewModel.java
@@ -4,8 +4,8 @@
 
 import com.example.sprout.refactor.common.ActivityEvent;
 import com.example.sprout.refactor.contract.ViewContract;
+import com.example.sprout.refactor.notification.Observer;
 import com.example.sprout.refactor.repository.RegistrationRepository;
-import com.example.sprout.refactor.repository.Repository;
 import com.example.sprout.refactor.util.PreferenceUtil;
 import com.example.sprout.refactor.vo.Account;
 
@@ -19,10 +19,28 @@
     private ObservableField<String> editUserName = new ObservableField<>("");
     private ViewContract viewContract = null;
     private RegistrationRepository registrationRepository = null;
+    private Observer<Account> observer = null;
 
     public RegistrationViewModel(RegistrationRepository registrationRepository, ViewContract toastContract) {
         this.registrationRepository = registrationRepository;
         this.viewContract = toastContract;
+        observer = new Observer<Account>() {
+            @Override
+            public void notify(Account account) {
+                PreferenceUtil.getInstance().saveInt(PreferenceUtil.Key.USER_ID, account.getUserID());
+                PreferenceUtil.getInstance().saveBoolean(PreferenceUtil.Key.REGISTERED, true);
+                viewContract.showShortToast("アカウントを作成しました");
+                viewContract.startActivity(ActivityEvent.START_ROOM_LIST);
+                viewContract.finishActivity();
+            }
+
+            @Override
+            public void error(Throwable throwable) {
+                viewContract.showShortToast("アカウント作成に失敗しました");
+
+            }
+        };
+        registrationRepository.getAccountObservable().addObserver(observer);
     }
 
     @Override
@@ -34,26 +52,18 @@
         }
     }
 
+    @Override
+    public void onDestroy() {
+        super.onDestroy();
+        registrationRepository.getAccountObservable().removeObserver(observer);
+    }
+
     public void onClickRegistration(String userName) {
         if (userName.isEmpty()) {
             viewContract.showShortToast("名前を入力して下さい");
             return;
         }
-        registrationRepository.registration(userName, new Repository.Listener<Account>() {
-            @Override
-            public void onSuccess(Account account) {
-                PreferenceUtil.getInstance().saveInt(PreferenceUtil.Key.USER_ID, account.getUserID());
-                PreferenceUtil.getInstance().saveBoolean(PreferenceUtil.Key.REGISTERED, true);
-                viewContract.showShortToast("アカウントを作成しました");
-                viewContract.startActivity(ActivityEvent.START_ROOM_LIST);
-                viewContract.finishActivity();
-            }
-
-            @Override
-            public void onFailure(Throwable throwable) {
-                viewContract.showShortToast("アカウント作成に失敗しました");
-            }
-        });
+        registrationRepository.registration(userName);
     }
 
     public ObservableField<String> getEditUserName() {