An electric supply device for a high-pressure discharge lamp comprising: an electric supply device control unit, having a function of switching between a steady lighting mode and a low power lighting mode in which electric power lower than the electric power in the steady lighting mode is supplied to the high pressure discharge lamp. While in the low power lighting mode, predetermined base current is continuously supplied to the high pressure discharge lamp and a current supply command signal is sent so that boost current obtained by superimposing current having a predetermined magnitude on the base current, is periodically supplied thereto, and a luminance control signal for adjusting the luminance of a video signal of a liquid crystal projector apparatus according to a magnitude of the electric power of the high pressure discharge lamp, which is operated responding to the supply of the boost current, is sent.