To make a circuit compact and inexpensive and reduce production of higher harmonic noises and acoustic noises from an incandescent lamp.

In a timing generating part 7, the zero-cross point of an ac power supply 1 is detected, and an ignition pulse is produced in every half-cycle at the timing corresponding to a dimming level provided through a transmission line 10, to make a LED emit light and to turn a light intercepting element PTH on. Thereby a thyristor 3 is turned on in every half-cycle. Therefore, a full-wave rectification voltage is supplied from a full-wave rectifier circuit 4 to an incandescent lamp 13 in every half-cycle, only for a period corresponding to the dimming level, to achieve dimmed lighting. In this case, an IGBT 5 is gradually turned on by a base control signal from an inclination control part 9 immediately before the rise of the ignition pulse, and therefore the rise of the voltage applied to the incandescent lamp 13 is slowed. Therefore, dimmed lighting of the incandescent lamp 13 can be achieved only by the phase control of one thyristor 3, and production of higher harmonic noises and acoustic noises from the incandescent lamp can be reduced.