PURPOSE: To provide the phase modulation circuit in which a degree of freedom of setting of a deviation of a phase of an output signal from a reference clock is enhanced.

CONSTITUTION: A voltage controlled oscillator circuit 4 in the phase modulation circuit provided with the voltage controlled oscillator circuit 4 receiving a reference clock, a phase comparator circuit 2 detecting a phase difference between the reference clock and an output of the voltage controlled oscillator circuit 4 and a low pass filter 3 integrating an output of the phase comparator circuit 2 and outputting the integrated circuit for a control signal of the voltage controlled oscillator circuit 4 is made up of N-stages of ring oscillators employing even number of conduction resistor controlled CMOS inverters 41-44 and odd number of usual CMOS inverters 49 and a signal subject to phase conversion is outputted from each stage of the ring oscillator.