To provide a mobile phone that can properly return to the inside of a communication zone.

A control processing section 7 decides the remaining capacity of a battery 6a, by measuring an output voltage of the battery 6a or by other methods, when discriminating unavailability of a waiting available channel. The control processing section 7 decides a time interval to execute retrieval of a perch channel, on the basis of the decided residual capacity of the battery 6a. The time interval for executing the retrieval of the perch channel is decided to be longer as the shorten the remaining capacity of the battery 6a becomes. The control processing section 7 starts a clock section 7a to measure an elapsed time and starts again a communication processing section 2 to execute the retrieval of the perch channel, after the lapse of a time in response to the time interval.