A device includes a direct current power circuit configured to convert an alternating current voltage from an alternating current power source into a direct current voltage, an output unit configured to convert a direct current from the direct current power circuit into a square wave alternating current whose polarity is inverted at a prescribed frequency and to supply the square wave alternating current to a high-pressure discharge lamp, a controller, and an anomaly detector configured to detect an instantaneous voltage drop of the alternating current power source. When the anomaly detector detects the instantaneous voltage drop, the controller switches from a normal lighting mode of controlling the output unit to supply the high-pressure discharge lamp with a square wave alternating current to a lighting maintained mode of controlling the output unit to supply the high-pressure discharge lamp with a square wave alternating current having a lower frequency than the square wave alternating current in the normal lighting mode. In this way, it is possible to maintain lighting of the high-pressure discharge lamp even upon occurrence of an instantaneous power failure, an instantaneous voltage drop, and the like.