この手順を正確に実行しましたか?
Create a Facebook Application
Request https://graph.facebook.com/oauth/authorize?client_id=MY_API_KEY& redirect_uri=http://www.facebook.com/connect/login_success.html& scope=publish_stream,create_event
Facebook will redirect you to http://www.facebook.com/connect/login_success.html? code=MY_VERIFICATION_CODE
Request https://graph.facebook.com/oauth/access_token?client_id=MY_API_KEY& redirect_uri=http://www.facebook.com/connect/login_success.html& client_secret=MY_APP_SECRET&code=MY_VERIFICATION_CODE
Facebook will respond with access_token=MY_ACCESS_TOKEN