Provided are an interworking procedure with an external network in a WLAN, a station supporting the interworking procedure, and a message format for the interworking procedure. In the interworking procedure, a non-AP station transmits a request message which includes an advertisement protocol ID set to a value indicating native query protocol and a native query information ID set to a value indicating emergency call number information. And the non-AP station receives from an access point (AP) a response message including zero or more emergency call numbers in response to the request message.