PURPOSE: To execute the automatic frequency control which is stable, and also, necessitates no adjustment even against the influence of a temperature fluctuation, etc., by comparing a demodulation output and the output of a sample-hold circuit, and executing the frequency stabilizing control of an FM modulator in accordance with its difference.

CONSTITUTION: A reference oscillation circuit 11, and an FM demodulating circuit 12 for executing FM demodulation of this oscillation output are provided, and an output voltage of this demodulating circuit 12 comes to a reference voltage of a comparing circuit 9. As a result, the reference voltage of the comparing circuit comes to a voltage obtained by demodulating an oscillation frequency of the reference oscillation circuit 11 by the FM demodulating circuit 12, therefore, the frequency by the reference oscillation circuit comes to a reference signal of the whole automatic frequency control circuit, and the system can be stabilized. Also, the temperature fluctuation of an FM demodulating circuit 7 is offset automatically by the temperature fluctuation of this FM demodulating circuit 12 since the FM demodulating circuit 12 is provided on a reference generation voltage side, and no-adjustment can be realized.