A third signal having a phase intermediate between a first signal based on a reference signal and a second signal with a phase shifted by an element of a previous stage is generated, a signal obtained by shifting the phase of the third signal by a first phase shill amount is output as a second signal to an element of a subsequent stage, a phase difference between the third signal and a fourth signal obtained by shifting the phase of a first signal output from the element of the subsequent stage by the first phase shift amount is detected, and the first phase shift amount is controlled on the basis of the detected phase difference.