PURPOSE: To correspond to temp. and even power source voltage change, to easily execute IC conversion and to make a system small.

CONSTITUTION: Immediately before the power source of a phase locked loop circuit 10 is turned on or an oscillation frequency changes, the control voltage of a voltage control oscillation circuit 3 is A/D converted by an A/D converter 20 so as to be stored in a storage means 30. Then, immediately after the power source of the phase synchronization loop circuit 10 is turned off or the oscillation frequency changes, control voltage data stored in a storage device 30 is read, analogically outputted from a DA converting means inside the A/D converter and inputted as the control voltage of the voltage control oscillation circuit 3 by executing disconnection between the low-pass filter 2 and the voltage control oscillation circuit 3 of the above phase locked loop circuit 10.