diff --git a/Colombia/Sources/APIClient/APIClient.swift b/Colombia/Sources/APIClient/APIClient.swift
index 8fa970e..0ae8506 100644
--- a/Colombia/Sources/APIClient/APIClient.swift
+++ b/Colombia/Sources/APIClient/APIClient.swift
@@ -19,17 +19,18 @@ struct APIClient {
             let url = requestable.url
             let request = URLRequest(url: url)
             let task = URLSession.shared.dataTask(with: request) { resultData, response, error in
-                guard let resultData = resultData else {
-                    if let error = error {
-                        observer.onError(error)
-                    }
+                if let error = error {
+                    observer.onError(APIError.unknown(error))
+                }
+                guard let resultData = resultData, response != nil else {
+                    observer.onError(APIError.response)
                     return
                 }
                 do {
                     let decodeData = try decoder.decode(T.Response.self, from: resultData)
                     observer.onNext(decodeData)
                 } catch let error {
-                    observer.onError(error)
+                    observer.onError(APIError.decode(error))
                 }
             }
             task.resume()
@@ -37,3 +38,9 @@ struct APIClient {
         }
     }
 }
+
+enum APIError: Error {
+    case decode(Error)
+    case response
+    case unknown(Error)
+}
diff --git a/Colombia/Sources/APIClient/AnnictAPIRequest.swift b/Colombia/Sources/APIClient/AnnictAPIRequest.swift
index af028c7..116c0e9 100644
--- a/Colombia/Sources/APIClient/AnnictAPIRequest.swift
+++ b/Colombia/Sources/APIClient/AnnictAPIRequest.swift
@@ -21,7 +21,7 @@ enum AccessToken {
 }
 
 enum Endpoint {
-    //とりあえずworksだけ実装
+    // TODO: とりあえずworksだけ実装
     case works
     
     func endpoint() -> String {
@@ -45,9 +45,9 @@ struct AnnictAPIRequest:Requestable {
         switch endpoint {
         case .works:
             baseURL.queryItems = [
-                //1ページあたりのデータの数、とりあえず20を指定
+                // TODO: 1ページあたりのデータの数、とりあえず20を指定
                 URLQueryItem(name: "per_page", value: "20"),
-                //とりあえずid,title,recommended_urlのみを受け取る
+                // TODO: とりあえずid,title,recommended_urlのみを受け取る
                 URLQueryItem(name: "fields", value: "id,title,images"),
                 URLQueryItem(name: "access_token", value: AccessToken.annictAPI)
             ]