PURPOSE: To reduce the call loss rate of a call which requires plural channels by selecting idle channels so that the number of the idle channels in respective time units are averaged when the new call arises.

CONSTITUTION: A call control management part 5 firstly designates a carrier f1 in an intra-carrier idle channel retrieval part 9 and it retrieves the positions of the idle channels in the carrier f1 by using a channel management table 7. When there is the idle channels in channels tm and f1, the call control management part 5 designates a time unit tm, a transmission station number (i) and a reception station number (j) in a use channel number measurement part 6. The use channel number measurement part 6 checks the presence or absence of the transmission of a transmission station 2i and the presence or absence of the reception of a reception station 2j in tm by using the channel management table 7. Consequently, the idle channels tm and fi are selected and they are assigned to the new call when the transmission station 2i is not used for transmission and the reception station is not used for reception. Thus, the call loss rate is reduced.