A cordless telephone system constituted by a switching station connected to a cable telephone exchanger and at least one telephone set connected to the switching station via a plurality of radio channels. The switching station has a controller which scans the radio channels and selects a nonused radio channel in response to a calling signal from the telephone exchanger, a signal generator for calling a telephone set, a signal detector for detecting a response signal from the telephone set, and a transmitter. The controller changes the number of radio channels to be scanned in accordance with the frequency of use of the radio channels and the transmitter sends a signal representing a changed number of radio channels. Each telephone set has a controller for scanning the radio channels, a signal detector for detecting the calling signal and the signal representing the number of channels from the switching station, and a transmitter for sending a response signal to the switching station.