To provide a duty decision circuit capable of varying a duty decision point.

This circuit is provided with an up-down counter with codes which counts up/down with count clocks according to the high level/low level of input signals and an up-counter and the prescribed ratio value of the count value of the up-counter is added to the count value of the up-down counter with the codes, by which the setting of the duty decision point at a desired point is made possible and even when the period of the input signals fluctuates, the duty decision is made possible without external control of a CPU, etc., after passing one period of input signals.