PURPOSE: To provide a synchronism deciding system for FM receiver which has the high reliability for decision of the synchronism and furthermore has not to set the transmission time in consideration of the responsiveness of a carrier sense circuit.

CONSTITUTION: A synchronizing circuit 6 decides whether the pattern of the signal received from a demodulation circuit 3 via a comparator 4 is coincident with the pattern of a synchronizing signal or not through the synchronization processing. When the synchronism is confirmed through the synchronization processing, the circuit 6 decides the presence or absence of a received signal based on the deciding output of a carrier sense circuit 5. When the presence of the received signal is decided, the circuit 6 confirms the synchronization and reads a series of data following the synchronizing signal and processes these data.