A projector device adapted to project an image-forming beam using a lamp as a light source. The lamp is installed within a rectangular parallelepipedal housing, and an exhaust fan is disposed to the rear of the lamp. The top wall of the housing surrounding the lamp is given an opening pattern asymmetric about the optical axis of the lamp by forming an air inlet opening in a position deviated from the optical axis toward a direction orthogonal to the axis for producing a swirling air current within the housing by operating the exhaust fan. The lamp can be effectively cooled with reduced quantities of air.