A retractable extension socket includes an socket body, a fixing structure, a receiving structure, a conducting wire and a plug. The fixing structure and the receiving structure are disposed on the socket body. One end of the conducting wire is connected to the socket body. The plug is connected to the other end of the conducting wire. Thus, a retractable extension socket is formed. The retractable extension socket can be used as an extension socket. In addition, by winding the cable into the socket body and attaching the plug into the fixing structure, the retractable extension socket can be used as a single plug. Furthermore, the plug can be collected into the receiving structure in order that it can be carried around easily.