PURPOSE: To improve the transmission distortion without causing any deterioration in selectivity, by subtracting the adding an audio signal FM-detected through a BPF from and to a signal halving the amplitude of the audio signal FM-detected further through a BPF having the same characteristic.

CONSTITUTION: An IF signal is inputted to the BPF22, a disturbing signal is eliminated and a transmission distortion D is generated. A modulation spectrum component at an output terminal of the BPF22 is expressed as S+D when S is a modulation signal. When the distortion of a detector 29 is small, the FM detection output becomes S+D also. This output is inputted to a non-inverting input of a subtractor 30. On the other hand, an output of the BPF22 inputted to an IF amplifier 23 is inputted to a BPF24 after amplification. When the characteristics of the BPFs 22, 24 are equal to those of the amplitude and phase, the output modulation spectrum component of the BPF24 is expressed approximately as S+2D. The output of the BPF24 is amplified and FM- detected, and the amplitude of S+2D is halved by an attenuator 27, 1/2S+D is inputted to an inverting input of the subtractor 30, where the signal is subtracted from the S+D at the non-inverting input, the 1/2S is outputted and a signal having no transmission distortion D is obtained.