A disclosed optical element includes: a transparent substrate; a subwavelength structure layer disposed on the transparent substrate, the subwavelength structure layer having a refractive index different from a refractive index of the transparent substrate; a minute concave and convex structure of one-dimensional grating formed on the subwavelength structure layer with a subwavelength period smaller than a wavelength to be used, where a concave portion reaches a boundary surface between the transparent substrate and the subwavelength structure layer; and an open hole portion formed on a subwavelength structure layer side of the transparent substrate so as to communicate with the concave portion of the minute structure and to be arranged with the same period as in the minute structure of one-dimensional grating. At least at the open hole portion, a refractive index relative to an incident light is changed in a direction orthogonal to the boundary surface.