A portable terminal having a Session Initiation Protocol, SIP, telephone call application installed therein for using the portable terminal as a cordless extension unit of a cordless telephone system, said portable terminal comprising: a reading unit for reading a medium recording first operating environment setting information required for connecting the portable terminal and a relay device by wireless under a first wireless standard; a first terminal side operating environment setting unit for analyzing the medium read by the reading unit, and acquiring the first operating environment setting information required for setting wireless connection under the first wireless standard and setting the first operating environment setting information to the portable terminal; a setting information generating unit for generating second operating environment setting information required to connect the portable terminal and the relay device to a SIP telephone call control server under a second wireless standard in order to make a call; a second terminal side operating environment setting unit for setting the second operating environment setting information generated by the setting information generating unit to the portable terminal, and transmitting the second operating environment setting information to the SIP telephone call control server and registering the second operating environment setting information therein; and a setting information transmitting unit for transmitting the second operating environment setting information to the relay device by utilizing the wireless connection set by the first terminal side operating environment setting unit in order to set, to the relay device, the second operating environment setting information generated by the setting information generating unit. a reading unit for reading a medium recording first operating environment setting information required for connecting the portable terminal and a relay device by wireless under a first wireless standard; a first terminal side operating environment setting unit for analyzing the medium read by the reading unit, and acquiring the first operating environment setting information required for setting wireless connection under the first wireless standard and setting the first operating environment setting information to the portable terminal; a setting information generating unit for generating second operating environment setting information required to connect the portable terminal and the relay device to a SIP telephone call control server under a second wireless standard in order to make a call; a second terminal side operating environment setting unit for setting the second operating environment setting information generated by the setting information generating unit to the portable terminal, and transmitting the second operating environment setting information to the SIP telephone call control server and registering the second operating environment setting information therein; and a setting information transmitting unit for transmitting the second operating environment setting information to the relay device by utilizing the wireless connection set by the first terminal side operating environment setting unit in order to set, to the relay device, the second operating environment setting information generated by the setting information generating unit.