diff --git a/action.yml b/action.yml
index b77f2fb..d07a6d6 100644
--- a/action.yml
+++ b/action.yml
@@ -12,22 +12,9 @@ inputs:
   roomId:
     required: true
     description: "Chatroom ID"
-  # deprecated inputs. this inputs parameter will be removed in the future version.
-  messageType:
-    description: "Message type to send. default is message."
-    type: "choice"
-    default: "message"
-    required: false
-    options:
-      - "message"
-      - "task"
   message:
     required: true
     description: "Message to send"
-  # deprecated inputs. this inputs parameter will be removed in the future version.
-  userIdsToAssignTask:
-    required: false
-    description: "User Id to be assigned to the task. Or you can specify multiple users, separated by commas. example 1,3,5"
 
 runs:
   using: "composite"
@@ -38,11 +25,6 @@ runs:
         fetch-depth: 0
     - name: "set up ruby"
       uses: "ruby/setup-ruby@v1"
-    - name: "deprecate messageType"
-      if: ${{ !github.event.inputs.messageType }}
-      run: |
-        echo "::warning::messageType is now deprecated. If you use only message, just remove the parameter. Or if you use task, please use okuzawats/chatwork-task-action instead. In this case, remove userIdsToAssignTask parameter also."
-      shell: "sh"
     - name: "run action"
       run: |
         ruby $GITHUB_ACTION_PATH/main.rb
@@ -51,5 +33,3 @@ runs:
         API_TOKEN: "${{ inputs.apiToken }}"
         ROOM_ID: "${{ inputs.roomId }}"
         MESSAGE: "${{ inputs.message }}"
-        MESSAGE_TYPE: "${{ inputs.messageType }}"
-        USER_IDS_TO_ASSIGN_TASK: "${{ inputs.userIdsToAssignTask }}"
diff --git a/main.rb b/main.rb
index 6fb22d8..b755f6c 100644
--- a/main.rb
+++ b/main.rb
@@ -4,51 +4,19 @@
   token: ENV['API_TOKEN'],
   room_id: ENV['ROOM_ID'],
   message: ENV['MESSAGE'].delete_prefix('"').delete_suffix('"'),
-  message_type: ENV['MESSAGE_TYPE'],
-  user_ids_to_assign_task: ENV['USER_IDS_TO_ASSIGN_TASK']
 }
 
-# message type must be message or task.
-type = params[:message_type]
-valid_types = ["message", "task"]
-unless valid_types.include?(type)
-  raise StandardError.new("type should be message or task.")
-end
-
-if params[:message].empty?
-  raise StandardError.new("empty message is not allowed.")
-end
-
-if type == "message"
-  uri = URI.parse("https://api.chatwork.com/v2/rooms/#{params[:room_id]}/messages")
-  http = Net::HTTP.new(uri.host, uri.port)
-  http.use_ssl = true
-
-  body = "body=#{params[:message]}"
-  headers = { "X-ChatWorkToken" => "#{params[:token]}" }
-
-  response = http.post(uri.path, body, headers)
-
-  if response.code == '200'
-    puts response.body
-  else
-    raise StandardError.new("action failed! #{response.body}")
-  end
-end
-
-if type == "task"
-  uri = URI.parse("https://api.chatwork.com/v2/rooms/#{params[:room_id]}/tasks")
-  http = Net::HTTP.new(uri.host, uri.port)
-  http.use_ssl = true
+uri = URI.parse("https://api.chatwork.com/v2/rooms/#{params[:room_id]}/messages")
+http = Net::HTTP.new(uri.host, uri.port)
+http.use_ssl = true
 
-  body = "body=#{params[:message]}&to_ids=#{params[:user_ids_to_assign_task]}"
-  headers = { "X-ChatWorkToken" => "#{params[:token]}" }
+body = "body=#{params[:message]}"
+headers = { 'X-ChatWorkToken' => params[:token].to_s }
 
-  response = http.post(uri.path, body, headers)
+response = http.post(uri.path, body, headers)
 
-  if response.code == '200'
-    puts response.body
-  else
-    raise StandardError.new("action failed! #{response.body}")
-  end
+if response.code == '200'
+  puts response.body
+else
+  raise StandardError, "action failed! #{response.body}"
 end