A lighting device for high-pressure discharge lamp for lighting the high-pressure discharge lamp by lowering or raising a DC voltage applied to an input side by a DC/DC converter circuit, then converting the DC power into an AC power by a DC/AC inverter circuit, supplying the AC power to the high-pressure discharge lamp and lighting the high-pressure discharge lamp, wherein when the polarity of the current of the high-pressure discharge lamp lit by the substantially rectangular wave is inverted, the output voltage of the DC/DC converter circuit is set to 1.5 times or more as large as the voltage at the stable lighting time of the high-pressure discharge lamp.