PURPOSE: To realized a stable automatic frequency control loop in the automatic frequency control circuit.

CONSTITUTION: A phase comparator 4 compares a phase of an output signal from a mixer 10 with a phase of a reference frequency signal from reference frequency oscillator sections 1, 8 and outputs an analog error signal representing frequency difference ±α. An A/D converter 5 converts the error signal into a digital error signal. A CPU 6 calculates a change in a locally oscillated frequency required to correct a frequency deviation from the digital error signal and outputs a digital value corresponding to the change in the local oscillation frequency. D/A converters 18, 19 convert the digital value respectively into a rough-adjustment analog value and a fine-adjustment analog value. Adder circuits 20-23 add the rough-adjustment analog value and the fine-adjustment analog value. Voltage controlled oscillator sections 2, 3 give a local oscillation frequency signal having a local oscillation frequency changed by a change corresponding to the added analog values to the mixer 10, from which a signal corrected by the frequency deviation is outputted.