Abstract: A light beam scanning device has a light source, a condenser optical system, a light beam deflector, and a light beam scanning lens. The light source radiates a light beam which is converted by the condenser optical system. The convergent light beam is then deflected at a constant angular velocity by the light beam deflector. The light beam scanning lens comprises a single lens, and the convergent light beam deflected by the light beam deflector is applied to the light beam scanning lens. The light beam scanning lens places the path of movement, caused by the light beam deflector, of a naturally focused spot where the convergent light beam converged by the condenser optical system is focused, and the scanned surface in substantially conjugate relationship. The light beam scanning lens also scans the scanned surface with the light beam at an approximately constant velocity.