In a multiplying circuit for providing a pulsed output clock signal having a frequency that is a multiple of a pulsed input clock signal, a delay of a digital delay line is initialized by initializing a counter when an external reset signal is input and when the number of pulses of the output clock signal from the clock generator is smaller than a predetermined multiplier. The delay of the digital delay line is set to a minimum value immediately following the initialization and then increased gradually in order to output the desired output clock signal.