PURPOSE: To decrease the number of elements by providing a voltage comparison circuit to compare an AFC signal with a reference voltage and a switching circuit switching the reference voltage at a constant voltage so as to simplify an AFC level detecting circuit.

CONSTITUTION: When a switch 101 is turned on, a tuning sweep voltage 211 starts rising, and a non-inverting terminal voltage of a voltage comparison circuit 103 rises by an S-shape curve characteristic of the AFC voltage As the circuit approaches a station, and when the voltage exceeds the reference voltage V1, a pulse is outputted accordingly, a differential signal is generated to reset a latch 104 and the rise of the tuning sweep voltage is stopped. Then the switch 102 is turned on, the descending of the tuning sweep voltage begins, and when the circuit approaches the station, the non-inverting voltage of the circuit 103 is descended by the S-shaped curve characteristic of the AFC voltage, and when the voltage is the reference voltage or below, a pulse is outputted, a differentiation signal is generated and a latch 105 is reset to stop the descending of the tuning sweep voltage.