A PWM signal generating circuit according to the invention includes a digital PWM signal generating circuit that generates a digital PWM signal having a resolution of 2n based on a clock signal CLK and n-bits (n.gtoreq.1) of digital information; a triangular wave generator that generates a triangular wave (e.g. ramp wave) synchronized with the clock signal CLK; and a comparator that compares the triangular wave with a threshold value. The PWM signal generating circuit increases the resolution of the digital PWM signal based on an output from the comparator.