A radio communication system in which information of a unit length is constituted with a plurality of frames as a set and the information is transmitted/received between a base station and a mobile station. A control section of the base station decides, during a telephone communications, performed between the base station and the mobile station, when an instruction to switch the frequency to a second frequency is received from an upper order network via a transmission/reception section, a time interval for the telephone communication using the second frequency so as not to stride over a boundary of frame sets adjacent to each other.