PURPOSE: To widen a PLL drawing range by providing the resonance circuit of a voltage control oscillator with the 1st and 2nd modulated-input terminals differing in modulation sensitivity and then by applying a phase error voltage to the 1st terminal and a modulated input signal to the 2nd terminal.

CONSTITUTION: A reference wave from reference frequency oscillator 11 is applied to phase comparator 12, the output of voltage control oscillator 14 is frequency- divided by frequency divider 15, and an obtained output is applied to comparator 12. Next, an error signal, corresponding to a phase difference, obtained by comparator 12 is band-limited by low-pass filter 13 and then applied to oscillator 14 by way of high-modulation-sensitivity input terminal 22 to which modulation- sensitivity-adjusting large capacitor 18 and modulating-voltage varactor diode 21 are connected in series. Simultaneously, a modulated input from modulation frequency oscillator 16 is applied to low-modulation-sensitivity input terminal 23, to which small capacitor 19 and voltage varactor diode 21 are connected in series, to generate a frequency-modulated waveform at modulated output 17.