To stabilize the response of a pulse-width modulation signal when an amplitude of an audio signal becomes excessive at a negative side.

A pulse-width modulation circuit 10 comprises: a clock generation circuit 11; a differential amplifier circuit 12; a first charge-current generation circuit 13; a second charge-current generation circuit 14; switches SW1 to SW4; capacitors C1 and C2; a first discharge constant-current circuit 15; a second discharge constant-current circuit 16; a first pulse generation circuit 17; a second pulse generation circuit 18; a pulse synthesis circuit 19; and a charge start voltage maintaining circuit 20. The charge start voltage maintaining circuit 20 prevents that charge start voltages of the capacitors C1 and C2 are lower than a voltage Va by supplying a power supply voltage to the capacitors C1 and C2 when the voltages of the capacitors C1 and C2 are almost lower than the voltage Va due to discharge operation by a constant current Id.