A serial input signal is sampled in synchronization with a plurality of first clock signals to obtain a plurality of sampling data pieces. A phase comparison circuit outputs a serial phase information signal based on the sampling data pieces. A serial-parallel conversion circuit performs a serial-to-parallel conversion on the serial phase information signal in synchronization with a second clock signal having a lower frequency, to output a parallel phase information signal. A digital filtering circuit calculates phase deviation and phase advance-delay signals based on the parallel phase information signal in synchronization with the second clock signal. By these signals, a phase control amount processing circuit generates a phase control signal. The phase control signal is in synchronization with third clock signals having a higher frequency. A phase interpolation circuit adjusts the phases of the third clock signals based on the phase control signal to output the first clock signals.