To obtain a pulse-width modulation output having narrow pulse width.

First and second triangular wave generating circuits 100 and 200 generate triangular waves TRI1 and TRI2 which are different 180° in the phase with each other and have the same crest value. A D/A converter 300 converts a digital image signal into an analog image signal DA1 having a maximum value a half as large as the triangular waves TRI1 and TRI2. Comparators 700 and 800 conduct pulse-width modulation on the DA1 by using TRI1 and TRI2 as reference signals to generate edge signals PWM1a and PWM1b. An AND circuit 900 ANDs PWM1a and PWM1b to generate a pulse-width modulated signal having its pulse width prescribed by PWM1a and PWM1b.