To correct self-excitation frequency error in an injection synchronizing oscillator when regenerating a clock using the injection synchronizing oscillator having a wide operating bandwidth.

An injection synchronizing oscillator 10 receives data from a data signal source and generates a clock signal in a self-excitation frequency. A phase comparator 20 detects a phase difference between the data from the data signal source and the clock signal. An integrator 30 integrates the phase difference from the phase comparator 20 and generates a control signal for controlling the self-excitation frequency of the injection synchronizing oscillator 10. A phase-locked loop is formed of the injection synchronizing oscillator 10, the phase comparator 20 and a filter 30.