A light source device for use in liquid crystal projectors which comprises a reflector oriented toward a liquid crystal panel and having a reflecting surface formed by a paraboloid or ellipsoid, and a light source disposed at the focal position of the reflector. A converter is disposed on an optical axis extending from the light source to the liquid crystal panel for converging light emanating from the light source and reflected from the reflector in accordance with the size of an image display portion of the panel. The reflecting surface of the reflector has a great focal distance so that the spreading angle of the reflected light is not greater than 8 deg.