PURPOSE: To correctly detect the phase difference even when the duty for a reference signal and a compared signal is not equal in a circuit for detecting the phase difference between the reference signal and the compared signal.

CONSTITUTION: A first flip flop 1 is provided, '1' is inputted to the data input, the reference signal is inputted to a clock input, a compared signal is inputted to a clear input, a second flip flop 2 is provided, the inverting output of a first flip flop is inputted to the data input, the compared signal is inputted to the clock input, and the reference signal is inputted to the clear input. Thus, the circuit for detecting the phase difference between the rising edges of the reference signal and the compared signal is constituted.