To simultaneously control plural dimmers.

Plural dimmers 18... once withhold control of an illumination load, when a control data signal to indicate simultaneous control of the illumination load is supplied, and start controlling by a control synchronizing signal. That is, when the illumination load is simultaneously controlled, a dimming table 11 has an address corresponding to each dimmer 18..., supplies the control data signal to indicate simultaneous control of the illumination load one by one to a master radio transmitter 13 to transmit it, and lastly transmits the control synchronizing signal. Thereby, the plural dimmers 18... are once in a waiting condition with the control date signal supplied, and start dimming control after the control synchronizing signal is supplied, therefore, plural illumination loads can be simultaneously controlled.