A projector includes a lamp drive circuit which drives a lamp, and a lamp drive current detection unit which detects the lamp drive current. Based upon the lamp drive current which is detected, the lamp drive circuit controls the lamp drive current by PWM control, so as to drive the lamp at constant power. A control unit detects the pulse width of this PWM control signal for the lamp several times, after a constant time period has elapsed from when the power supply is turned ON, and includes a lamp shorted out decision unit which decides that the lamp is shorted out, if all of these pulse widths which have thus been detected are less than or equal to a predetermined width.