A projector includes a casing, a light source, and a heat dissipation device. The light source and the heat dissipation device are installed inside the casing. Two openings are formed at two sides of the casing opposing to the light source. A light shield is positioned on one of the two openings. The light shield has a fixing plate, and a plurality of first parallel light-shielding plates and a plurality of second parallel light-shielding plates for blocking light leaking from the openings.