A lens is obtained by injection molding. The lens includes a plurality of projections arranged on a surface at a pitch smaller than or equal to a predetermined value to reduce reflection of light with a wavelength equal to or greater than the pitch, and a gate mark formed on an outer periphery of the optical element in the injection molding. A peripheral portion of the surface includes a first region whose circumferential position corresponds to the gate mark, and a second region being adjacent to the first region. Axes of first projections in the first region are inclined more outward than axes of second projections in the second region.