PURPOSE: To always obtain latest idle channel information without interrupting communication even if the communication time of a base station continues long by storing idle information informed from a mobile station and selecting a radio commuication channel based on the information in the base station.

CONSTITUTION: A communication equipment for mobile station is provided with an idle channel retrieval circuit part 20, a silence detection part 21 and a change-over switch 22 consisting of a transistor. A control part 15 is provided with a micro computer as a main control circuit, and is provided with a transmission stop control means, an idle channel retrieval control means and an idle channel information notice control means, for example. The mobile station detects the silence period of a transmitting voice signal, stops the transmission operation of a transmission period corresponding to the silence period, selectively receives plural radio frequencies in the stop period of the transmission operation, retreives the idle radio communication channel by the radio frequencies from the received result and gives the notice of a retrieval result to the base station.