Portable radio telephone and method for selecting radio channel of cheap fee

A radio telephone system is arranged by a communication network, a cordless telephone, and a plurality of public radio base stations, which are connected to the connected to the communication network, a portable terminal of this cordless telephone is communicatable with not only a radio base station of this cordless telephone, but also the plural public radio base stations. The portable terminal includes such a means (6; step S1-S4 of Fig. 2) for searching an ID code of a relevant radio base station contained in the received radio signal, and for judging whether or not the received radio signal corresponds to a radio signal transmitted from the cordless telephone to which this portable terminal belongs. The portable terminal causes the searching means to search the ID code when a power supply is turned ON and a telephone call is made. The portable terminal sets a radio channel between the radio base station for the cordless telephone to which this portable terminal belongs and this portable terminal when the ID code of the radio base station for this cordless telephone is detected. Thus, when a telephone call is made, a telephone communication can be made by the portable terminal via the radio base station of this cordless telephone, resulting in a low-cost telephone communication.