Disclosed is a lighting circuit for a vehicular lamp which cuts off power supply to the discharge lamp when the discharge lamp flickers due to the expiration of its service life or the like, thus ensuring safety for an approaching vehicle. In the lighting circuit for a metal halide lamp, when a lighting switch is set on, the battery voltage is boosted by a DC booster circuit and is then converted into an AC voltage by a DC/AC converter. This AC voltage is applied to the metal halide lamp. An abnormality detector is provided to detect that the lamp gets into a flickering state. When the output voltage of the DC booster circuit becomes greater than a threshold value after a predetermined wait time elapses from the point at which the output voltage has exceeded the threshold value, the abnormality detector determines this situation as abnormal lighting and sends a signal to a power cutoff relay circuit to stop supplying the battery voltage to the DC booster circuit.