PURPOSE: To reduce the amount of feedback when an FM input signal has a small frequency shift, and to obtain noise-improved demodulated picture quality, by inserting a nonlinear circuit into a feedback circuit for threshold improvement by a narrow band pass filter.

CONSTITUTION: An FM signal modulated by a color TV signal is inputted from a terminal 7 and demodulated through a variable narrow band pass filter 9, a limiter 3, and a discriminator 4, but part of the demodulated signal is fed back to the filter 9 through a low-pass filter 6 for the improvement of a threshold level. When the input FM signal has a small frequency shift, an FM noise component is fed back to cause deterioration in picture quality. To prevent that, a nonlinear circuit 10 which varies in input and output amplitude ratio with an input amplitude level is inserted into the feedback circuit and when the input FM signal has a small frequency shift, the amount of the feedback is reduced, thereby improving the SN ratio of the output demodulated signal.