To provide a lighting circuit of a projector that can be driven by both the commercial alternating-current power supply and a battery and is convenient for portable use. A lighting circuit for a high-pressure discharge lamp 14 includes: a DC/DC converter 1 that boosts a direct-current voltage and outputs the boosted direct-current voltage; an AC/DC converter 10 that rectifies an alternating-current voltage to output a direct-current voltage; an input switch circuit 2 and a power switch circuit 3 that switch between the DC/DC converter 1 and the AC/DC converter 10; a ballast circuit 11 that stabilizes the lighting of the high-pressure discharge lamp 14; a power control section 12 that controls the power supply from the ballast circuit 11 to the high-pressure discharge lamp 14; a lighting initiation circuit 13 that starts lighting of the high-pressure discharge lamp 14; and the high-pressure discharge lamp 14, and the power switch circuit 3 performs power switching in such a manner that a relatively low power is supplied to the high-pressure discharge lamp 14 when a direct-current power supply is connected only to the DC/DC converter, and a relatively high power is supplied to the high-pressure discharge lamp 14 when the commercial alternating-current power supply is connected to the AC/DC converter 10.