A control transistor is connected in parallel with an input transistor of a bias generation circuit in a voltage control delay circuit. A power supply potential Vcc is divided by voltage divider resistors to be applied to the gate of the control transistor. Reduction in the power supply potential Vcc causes reduction in a current Ib flowing to the control transistor, and a current Ic=Ia+Ib flowing to a delay time variable element. When the power supply potential Vcc is reduced, the factor of a delay time period of delay time variable elements becoming shorter due to a smaller amplitude of a clock signal is canceled with the factor of the delay time period of the delay time variable elements become longer due to a smaller current Ic flowing thereto. Therefore, variation in the delay time period can be suppressed to a low level.