A first optical system couples a light beam from a light source, including a first lens made of glass with a positive power and a second lens made of plastic with a negative power. A second optical system focuses the light beam from the first optical system onto a scanning surface and moves a light spot on the scanning surface in a main-scanning direction. One of an incidence plane and an output plane of the first lens is spherical while the other is spherical or flat. A cross-sectional plane of the second lens along one of the main-scanning direction and a sub-scanning direction has a non-arc shape on at least one of the incidence plane and the output plane.