A spread spectrum clock generator includes a phase comparator to detect a phase difference between a reference input clock signal and a feedback signal and output a control voltage, a voltage controlled oscillator to generate an output clock signal with a frequency in line with the control voltage, a phase selector to select any of equally divided phases of one cycle of the output clock signal, generate and transmit a phase shift clock signal to the phase comparator as the feedback signal, and a phase controller to decide a phase of the rising edge of the phase shift clock signal and control the phase selector to select the decided phase, and generate a second phase shift amount, decide the rising edge of the phase shift clock signal to and subject the output clock signal to spread spectrum modulation by the second phase shift amount.