In a discharge lamp lighting circuit 1, a control circuit 7 detects a failure in a discharge lamp 8 or the lighting circuit to stop supplying the power to the discharge lamp 8 or stop the operation of the lighting circuit, or lights another light source as a substitute light source for the discharge lamp and notifies the occurrence of a failure when the discharge lamp 8 can no longer be lit. A delay time generator circuit 31 is provided for a failure detection/determination circuit 22 such that the foregoing functions are prohibited until a predefined time period is elapsed after the time switch means SW1, SW2 are substantially simultaneously switched on to cause the lighting circuit to start operating.