To simplify wiring, supply electric power, and maintain a line in the always best efficiency condition by receiveing light dimming indication transmitted from a power source switch by a logical controller, outputting an intermittent electric power waveform in succession, and producing a light dimming effect by the discontinuous time ratio of output electric power.

An electronic ballast light dimming device contains a power source switch 43 and an electronic ballast 30, and the power source switch 43 transmits light dimming indication to the electronic ballast 30 by a method of temporarily interrupting a power source. The electronic ballast 30 is connected in order up to an oscillator 39 after being connected to a power source switch 43 from a wave filter 31, and also processes a signal of the power source transmitted up to be connected to a luminaire 40. A logical controller 37 not only receives light dimming indication transmitted from the power source switch 43 but also produces electric power having a temporary high frequency to the light dimming indication, and outputs it to the luminaire 40, and exhibits a light dimming effect. Therefore, in a light dirmming process, an adjustment of an electric resistance and an inductor are obviated, and excessive resistance is not caused, and the best efficiency is established.