diff --git a/sample.properties b/sample.properties
index d3305c4..1cdd664 100644
--- a/sample.properties
+++ b/sample.properties
@@ -4,3 +4,6 @@ API_BASE_URL     = https://partnerapi-sandbox.pokepay.jp
 
 PKCS12_FILE      = certkey.p12
 PKCS12_PASSWORD  = changeit
+
+ACCEPT-LANGUAGE = en
+
diff --git a/src/main/java/jp/pokepay/partnerapi/Config.java b/src/main/java/jp/pokepay/partnerapi/Config.java
index 9b41796..7eae1a6 100644
--- a/src/main/java/jp/pokepay/partnerapi/Config.java
+++ b/src/main/java/jp/pokepay/partnerapi/Config.java
@@ -9,6 +9,7 @@ class Config {
     public String baseUrl;
     public String p12File;
     public String p12Password;
+    public String acceptLanguage;
 
     public Config(File file) throws ConfigFileNotFoundException, ProcessingError {
         Properties properties = new Properties();
@@ -29,5 +30,6 @@ public Config(File file) throws ConfigFileNotFoundException, ProcessingError {
         this.baseUrl = properties.getProperty("API_BASE_URL");
         this.p12File = file.toPath().getParent().resolve(properties.getProperty("PKCS12_FILE")).toString();
         this.p12Password = properties.getProperty("PKCS12_PASSWORD");
+        this.acceptLanguage = properties.getProperty("ACCEPT-LANGUAGE", "en");
     }
 }
diff --git a/src/main/java/jp/pokepay/partnerapi/HttpClient.java b/src/main/java/jp/pokepay/partnerapi/HttpClient.java
index 285df9c..68ffed0 100644
--- a/src/main/java/jp/pokepay/partnerapi/HttpClient.java
+++ b/src/main/java/jp/pokepay/partnerapi/HttpClient.java
@@ -128,7 +128,7 @@ public Response get(String path, String body) throws ProcessingError, Connection
         }
     }
 
-    public Response post(String path, String body) throws ProcessingError, ConnectionError {
+    public Response post(String path, String body, String acceptLanguage) throws ProcessingError, ConnectionError {
         URL url = ensureURL(path);
         try {
             HttpURLConnection conn = openConnection(url);
@@ -137,7 +137,7 @@ public Response post(String path, String body) throws ProcessingError, Connectio
             conn.setRequestProperty("accept", "*/*");
             if (body != null) {
                 conn.setDoOutput(true);
-                conn.setRequestProperty("Accept-Language", "jp");
+                conn.setRequestProperty("Accept-Language", acceptLanguage);
                 conn.setRequestProperty("Content-Type", "application/json; charset=utf-8");
                 conn.setRequestProperty("Content-Length", String.valueOf(body.length()));
                 OutputStreamWriter out = new OutputStreamWriter(conn.getOutputStream());
diff --git a/src/main/java/jp/pokepay/partnerapi/PartnerAPI.java b/src/main/java/jp/pokepay/partnerapi/PartnerAPI.java
index 8568a32..41a6324 100644
--- a/src/main/java/jp/pokepay/partnerapi/PartnerAPI.java
+++ b/src/main/java/jp/pokepay/partnerapi/PartnerAPI.java
@@ -68,7 +68,7 @@ public String encodeRequest(Request request) throws ProcessingError {
     }
 
     public Response send(Request request) throws ProcessingError, ConnectionError, PartnerRequestError {
-        HttpClient.Response response = httpClient.post(request.path(), encodeRequest(request));
+        HttpClient.Response response = httpClient.post(request.path(), encodeRequest(request), config.acceptLanguage);
         JsonResponse json = gson.fromJson(response.getBody(), JsonResponse.class);
         if (json.responseData == null) {
             ErrorResponse errorResponse = gson.fromJson(response.getBody(), ErrorResponse.class);