A PWM control system, comprising PWM fundamental wave generation means for forming a PWM fundamental wave by dividing a fundamental frequency signal; PWM cycle setting means for setting a PWM cycle on the basis of the PWM fundamental wave; duty ratio formation means for forming a duty ratio (N/M:N.ltoreq.M, where M is the maximum number of clocks) in the PWM cycle; and PWM control signal output means for outputting a PWM control signal with the duty ratio to a load drive circuit.