To set a coefficient which is capable of a lock-in control near the center value of a voltage-controlled oscillator(VCO) control voltage to a coefficient multiplication circuit by providing the coefficient control circuit for supplying a coefficient setting signal, corresponding to the coefficient positioned near the reference value of control voltage to the coefficient multiplication circuit.

An unlocking detection circuit 25 sets an unlocking detection pulse 27 to an H-level, only when the phase shift of a first reference signal (horizontal synchronizing signal) H.REF and a comparison signal H.VARI continues for a prescribed period. A coefficient Q control circuit 26 detects a difference between VCO control voltage data 30 which is A/D-converted by an A/D converter 40 and the center value of VCO control voltage and detects an optimum setting value (VCO control voltage which approaches closest to center voltage). The control voltage 30 of the VCO oscillator 22 selects the coefficient capable of lock-in controll near the center of the control voltage range and is given to a coefficient multiplier 23 as the coefficient setting signal 29.