PURPOSE: To provide a phase synchronizing oscillator capable of lowering a phase noise even when it is used at a high frequency band concerning a phase synchronizing oscillator to be used in a frequency conversion part in a radio equipment.

CONSTITUTION: In the phase synchronizing oscillator having a phase comparing part 1 for comparing the phase of an inputted reference signal having prescribed frequency with phase of a comparing signal, extracting a phase difference and sending the phase difference through a low pass filter as a control signal, a voltage control oscillator 2 for sending an output signal with frequency corresponding to the inputted control signal and an N frequency dividing part 3 provided with the 1st frequency dividing part 31 for dividing the frequency of the output signal and the 2nd frequency dividing part 32 for further dividing the frequency of an output from the 1st part 31 and sending the frequency-divided result as a comparing signal, the frequency dividing ratio of the 1st part 31 is set up so that the output frequency of the part 31 is existed within the operation frequency range of the 2nd part 32, an element having operation speed slower than that of the 1st part 31 is used for the 2nd part 32 and the frequency dividing ratio of the 2nd part 32 is set up to N/ (frequency dividing ratio of the 1st frequency dividing part 31).