A collimator lens is configured with a double convex single lens formed with a resinous material, for collimating a light flux emitted from a light source. At least one of surfaces of the collimator lens is formed as an aspherical surface. The collimator lens satisfies following conditions: 2 0.6, where R1 is a curvature radius of a first surface, which is a lens surface on a side of the light source of the collimator lens, R2 is a curvature radius of a second surface, which is a lens surface on a side opposite to the first surface of the collimator lens, and NA is a numerical aperture on the side of the light source of the collimator lens.