PURPOSE: To obtain a synchronization detection circuit in which a signal from a detector is branched, one branched signal is subject to amplitude limit and the resulting signals are multiplied so as to eliminate distortion due to phase fluctuation of the signal.

CONSTITUTION: A detector 1 detects an AM modulation signal 7 and an amplifier 2 amplifies an output signal 8 of the detector 1. A limiter circuit 3 applies amplitude limit to an output signal 10 of the amplifier 2 and a delay circuit 4 corrects the delay by the amplifier 2 and a delay by the limiter circuit 3 and then a propagation delay. A multiplier 5 multiplies the output signal 1 of the limiter circuit 3 and an output signal 9 of the delay circuit 4 and a low pass filter 6 applies band limit to an output signal 12 of the multiplier 5.