diff --git a/README.md b/README.md
index 10747f7..353c0ca 100644
--- a/README.md
+++ b/README.md
@@ -4,12 +4,67 @@ Resize image by AWS Lambda
 ## Features
 
 * Use [Serverless Framework](https://github.com/serverless/serverless#features)
-* The image conversion procedure is as follows.
-  * You upload an image file to `s3://${SOURCE_S3_BUCKET_NAME}/${SOURCE_S3_PREFIX}/xxxx.png`.
-  * S3 create object-created event. and invoke AWS Lambda function.
-  * Downloads raw image file from s3 in AWS Lambda.
-  * Resize the image with ImageMagick(using [gm](https://github.com/aheckmann/gm))
-  * Uploads the resized image file to `s3://${DEST_S3_BUCKET_NAME}/${DEST_S3_PREFIX}/{26 random chars}.{png|jpg|gif|...}` in AWS Lambda.
+* The image conversion by event of s3 object created
+* The image conversion endpoint by API Gateway
+
+### The image conversion by event of s3 object created
+
+* You upload an image file to `s3://${SOURCE_S3_BUCKET_NAME}/${SOURCE_S3_PREFIX}/xxxx.png`.
+* S3 create object-created event. and invoke AWS Lambda function.
+* Downloads raw image file from s3 in AWS Lambda.
+* Resize the image with ImageMagick(using [gm](https://github.com/aheckmann/gm))
+* Uploads the resized image file to `s3://${DEST_S3_BUCKET_NAME}/${DEST_S3_PREFIX}/{26 random chars}.{png|jpg|gif|...}` in AWS Lambda.
+
+### The image conversion endpoint by API Gateway
+
+Create converted image.
+
+#### URL
+
+* `https://{random}.execute-api.{region}.amazonaws.com/{stages}/api/v1.0/resized_image`
+  * `{random}`
+    * Random string determinated by serverless.
+  * `{region}`
+    * Region of AWS
+  * `{stages}`
+    * Stages of API Gateway deployed by serverless.
+
+#### Method
+
+`POST`
+
+#### Request
+##### Headers
+
+None.
+
+##### Parameters
+
+|Name|Type|Required|Detail|Example|
+|---|---|---|---|---|
+|`source_url`| string | true | URL of source image. | `s3://examples.com/image.png` |
+|`resize_option`| string | false | Resize option by imagemagick. See [Resizing or Scaling -- IM v6 Examples](http://www.imagemagick.org/Usage/resize/#resize) | `800x600` |
+|`dest_s3_bucket`| string | false | Destination of s3 bucket name | `upload-resized-image-bucket` |
+|`dest_s3_prefix`| string | false | Destination of s3 prefix | `upload` |
+
+#### Response
+##### Headers
+
+|Key|Value|
+|---|---|
+|`Content-Type`|`application/json`|
+
+##### Body
+
+```
+{
+  "ETag": "\"a2aeedc65cb3a9398a74801401092c8c\"",
+  "Location": "https://example-bucket.s3-ap-northeast-1.amazonaws.com/result/01BQCS8J09S1W7VBWCPZ1Z5Z3X.jpeg",
+  "key": "result/01BQCS8J09S1W7VBWCPZ1Z5Z3X.jpeg",
+  "Key": "result/01BQCS8J09S1W7VBWCPZ1Z5Z3X.jpeg",
+  "Bucket": "example-bucket"
+}
+```
 
 ## Required