An optical element includes a substrate including a first surface and metal structure group including a plurality of metal structures, the metal structures being arranged on the first surface in a two-dimensionally isolated manner. Light is incident on the metal structure group in an oblique manner with respect to the normal of the first surface from the metal-structure-group side or the substrate side, so that a polarization state of light that passes through the metal structure group and a polarization state of light that is reflected by the metal structure group differ from each other in accordance with a wavelength range.