To provide an opposite phase control dimmer with high performance capable of reducing surge voltage applied to a switching element, and realizing a size smaller and a price lower than the conventional opposite phase control dimmer.

This opposite phase control dimmer controls power applied to an incandescent lamp load L by opposite-phase-controlling AC power E with a semiconductor acting as a switching element (a), especially controls on.off timing at a 0 point, and has an excess current protecting function for continuing turning off to the next 0 point independent of a control signal when rush current in lighting reaches a previously set excess current level, and by increasing a time constant of a driving circuit of the switching element (a) only when excess current flows in lighting, the turn off time of the switching element is extended, and surge voltage being applied to the switching element (a) is decreased.