PURPOSE: To decrease surely the disturbance of intermodulation by using a level of a disturbing wave having the frequency relation where the ternary intermodulation product is caused in the same frequency as the frequency of a reception desired wave to control the gain of a receiver.

CONSTITUTION: A signal received through an antenna 1 and a high-frequency amplifier circuit 2 is outputted from a demodulation circuit 3 and also given to an undesired wave extracting circuit 4. The desired wave is trapped at the undesired wave extraction circuit 4, only the undesired wave is given to a multiplier circuit 5 comprising multipliers 51, 52, from which a cubic product is generated. An intermodulation disturbing wave extraction circuit 6 extracts the frequency component equal to that of the desired wave from the output of the multiplier circuit 5, a control signal generating circuit 7 generates a gain control signal S depending on the level to control the gain of the high-frequency amplifier circuit 2. Thus, the intermodulation disturbance is decreased accurately.