diff --git a/README.md b/README.md
index 95f6c85..3093436 100644
--- a/README.md
+++ b/README.md
@@ -53,8 +53,14 @@ $ npx prisma db seed
 ## テスト環境でのgithubログインの省略
 ```
 # user1 
-eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VySWQiOjEsImlhdCI6MTY1OTc3MDY1OX0.lpGGDVJ0y-IfAViLy5D8m8GY965ZqTxQ-TZgikrQ5ME
+Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VySWQiOjEsImlhdCI6MTY1OTc3MDY1OX0.lpGGDVJ0y-IfAViLy5D8m8GY965ZqTxQ-TZgikrQ5ME
 
 # user2
-eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VySWQiOjIsImlhdCI6MTY1OTc3MDY1OX0.tzLuKarW0wCOz-hI4xTQ5Q6S08NMZx3VWeKb4-9Cq4U
+Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VySWQiOjIsImlhdCI6MTY1OTc3MDY1OX0.tzLuKarW0wCOz-hI4xTQ5Q6S08NMZx3VWeKb4-9Cq4U
+
+# profile1
+Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VySWQiOjEsImNvbW11bml0eUlkIjoiY29tbXVuaXR5SWQxIiwicHJvZmlsZUlkIjoxLCJpYXQiOjE2NjIwMzI3Njh9.jtP9f1HtmTOaoE8o73jyRvsmp7LSaHxJoFv6dPYwD-c
+
+# profile4
+Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VySWQiOjIsImNvbW11bml0eUlkIjoiY29tbXVuaXR5SWQyIiwicHJvZmlsZUlkIjo0LCJpYXQiOjE2NjA0NzY0NTB9.5DCEP8ckjnagldmWWEPpUzGcuwNdDHVSa8xlCXXxoxs
 ```
diff --git a/api/nexus-typegen.ts b/api/nexus-typegen.ts
index 724d78e..ec1198c 100644
--- a/api/nexus-typegen.ts
+++ b/api/nexus-typegen.ts
@@ -227,7 +227,8 @@ export interface NexusGenFieldTypes {
     name: string; // String!
   }
   Subscription: { // field return type
-    waitForMessage: NexusGenRootTypes['Message'] | null; // Message
+    waitForMessage: NexusGenRootTypes['Message']; // Message!
+    waitForMessageNotification: NexusGenRootTypes['Post']; // Post!
   }
   User: { // field return type
     githubBio: string; // String!
@@ -348,6 +349,7 @@ export interface NexusGenFieldTypeNames {
   }
   Subscription: { // field return type name
     waitForMessage: 'Message'
+    waitForMessageNotification: 'Post'
   }
   User: { // field return type name
     githubBio: 'String'
diff --git a/api/schema.graphql b/api/schema.graphql
index 1f2498c..f33e671 100644
--- a/api/schema.graphql
+++ b/api/schema.graphql
@@ -125,7 +125,8 @@ type Skill {
 }
 
 type Subscription {
-  waitForMessage(postId: String!): Message
+  waitForMessage(postId: String!): Message!
+  waitForMessageNotification: Post!
 }
 
 type User {
diff --git a/api/src/context.ts b/api/src/context.ts
index 0c5d0aa..e179817 100644
--- a/api/src/context.ts
+++ b/api/src/context.ts
@@ -62,3 +62,36 @@ export const context = ({ req }: { req: Request }): Context => {
     },
   };
 };
+
+export const contextForWs = async (ctx: any, msg: any, args: any) => {
+  const token =
+    ctx && ctx.connectionParams && ctx.connectionParams.Authorization
+      ? decodeAuthHeader(ctx.connectionParams.Authorization)
+      : null;
+
+  return {
+    prisma,
+    userId: token?.userId,
+    profileId: token?.profileId,
+    communityId: token?.communityId,
+    pubsub,
+    expectUserLoggedIn(): UserLoggedInContext {
+      if (!this.userId) {
+        throw new Error("You have to log in");
+      }
+      return { prisma: this.prisma, pubsub: this.pubsub, userId: this.userId };
+    },
+    expectUserJoinedCommunity(): UserJoinedCommunityContext {
+      if (!this.userId || !this.profileId || !this.communityId) {
+        throw new Error("You have to join a community");
+      }
+      return {
+        prisma: this.prisma,
+        pubsub: this.pubsub,
+        userId: this.userId,
+        profileId: this.profileId,
+        communityId: this.communityId,
+      };
+    },
+  };
+};
diff --git a/api/src/graphql/Message.ts b/api/src/graphql/Message.ts
index 1d69908..759a742 100644
--- a/api/src/graphql/Message.ts
+++ b/api/src/graphql/Message.ts
@@ -57,15 +57,11 @@ export const MessageQuery = extendType({
         if (!post) {
           throw new Error("post doesn't exist");
         }
-        if (profileId != post.driverId && profileId != post.navigatorId) {
-          throw new Error("no right to see messages");
-        }
+        validateOwnership(profileId, post);
 
         return await context.prisma.message.findMany({
           where: { postId },
-          orderBy: {
-            createdAt: "asc",
-          },
+          orderBy: { id: "asc" },
         });
       },
     });
@@ -85,6 +81,14 @@ export const MessageMutation = extendType({
         const { postId, content } = args;
         const { profileId } = context.expectUserJoinedCommunity();
 
+        const post = await context.prisma.post.findUnique({
+          where: { id: postId },
+        });
+        if (!post) {
+          throw new Error("post doesn't exist");
+        }
+        validateOwnership(profileId, post);
+
         const newMessage = await context.prisma.message.create({
           data: {
             post: {
@@ -96,8 +100,16 @@ export const MessageMutation = extendType({
             },
           },
         });
+        const opponentId = (
+          post.driverId == profileId ? post.navigatorId : post.driverId
+        ) as number;
+
         // todo: is 'await' necessary? (https://codesandbox.io/s/nexus-example-subscriptions-59kdb?file=/src/schema/index.ts)
         await context.pubsub.publish(postId.toString(), newMessage);
+        await context.pubsub.publish(
+          "messageNotification:" + opponentId.toString(),
+          post
+        );
         return newMessage;
       },
     });
@@ -116,9 +128,7 @@ export const MessageMutation = extendType({
         if (!post) {
           throw new Error("post doesn't exist");
         }
-        if (profileId != post.driverId && profileId != post.navigatorId) {
-          throw new Error("no right to see messages");
-        }
+        validateOwnership(profileId, post);
 
         const where = { postId, createdById: { not: profileId } };
         await context.prisma.message.updateMany({
@@ -138,18 +148,46 @@ export const MessageMutation = extendType({
 export const MessageSubscription = subscriptionType({
   definition(t) {
     // todo: should it be non-nullable?
-    t.field("waitForMessage", {
+    t.nonNull.field("waitForMessage", {
       type: "Message",
       args: {
         postId: nonNull(stringArg()),
       },
-      subscribe(parent, args, context) {
+      async subscribe(parent, args, context) {
         const { postId } = args;
+        const { profileId } = context.expectUserJoinedCommunity();
+        const post = await context.prisma.post.findUnique({
+          where: { id: postId },
+        });
+        if (!post) {
+          throw new Error("post doesn't exist");
+        }
+        validateOwnership(profileId, post);
+
         return context.pubsub.asyncIterator(postId);
       },
       async resolve(messagePromise: Promise<Message>) {
         return await messagePromise;
       },
     });
+
+    t.nonNull.field("waitForMessageNotification", {
+      type: "Post",
+      subscribe(parent, args, context) {
+        const { profileId } = context.expectUserJoinedCommunity();
+        return context.pubsub.asyncIterator(
+          "messageNotification:" + profileId.toString()
+        );
+      },
+      async resolve(postPromise: Promise<Post>) {
+        return await postPromise;
+      },
+    });
   },
 });
+
+const validateOwnership = (profileId: number, post: Post) => {
+  if (profileId != post.driverId && profileId != post.navigatorId) {
+    throw new Error("no right to see messages");
+  }
+};
diff --git a/api/src/index.ts b/api/src/index.ts
index ab6468c..ec61966 100644
--- a/api/src/index.ts
+++ b/api/src/index.ts
@@ -7,7 +7,7 @@ import { WebSocketServer } from "ws";
 import { useServer } from "graphql-ws/lib/use/ws";
 import { ApolloServerPluginLandingPageLocalDefault } from "apollo-server-core";
 
-import { context } from "./context";
+import { context, contextForWs } from "./context";
 import { schema } from "./schema";
 
 const app = express();
@@ -18,7 +18,7 @@ const wsServer = new WebSocketServer({
   path: "/graphql",
 });
 
-const serverCleanup = useServer({ schema, context }, wsServer);
+const serverCleanup = useServer({ schema, context: contextForWs }, wsServer);
 
 const server = new ApolloServer({
   schema,