A lighting device for an ac-lighting type ultra-high pressure mercury lamp includes:
a stepdown chopper for converting dc voltage that is supplied from the outside
to voltage of a prescribed level; a full-bridge switch circuit for generating either
dc or ac voltage from the output voltage of the stepdown chopper and supplying
the generated voltage to the ultra-high pressure mercury lamp; and a control circuit
for controlling the full-bridge switch circuit such that, when extinguishing the
lamp, a dc voltage is supplied over a prescribed time interval with a prescribed
electrode of the ultra-high pressure mercury lamp as the anode.