PURPOSE: To provide a synthesizer assigning method for channel switching which is stably operated by making the same channel use the same synthesizer.

CONSTITUTION: With respect to the synthesizer assigning method for channel switching where two synthesizers are switched by a changeover switch to supply a prescribed frequency signal to each channel in the communication machine which is provided with two synthesizers and a changeover switch and has four channels of the time division multiplexing system, synthesizers A1 and B2 are alternately switched by the changeover switch 3 and are successively assigned to four channels at the time of switching the channels in time division, and thereby, the same synthesizer is always assigned to the same channel.