An optical unit having an antireflection function includes a wave surface having a wavelength equal to or shorter than a wavelength of visible light. The wave surface has a curved plane which curves in a recessed shape between an apex portion and a bottom portion of the wave surface. An inflection point of an area of a cross section obtained by cutting through the wave surface in a plane perpendicular to a direction of vibration of the wave surface is positioned toward the bottom portion of the wave surface from a center of the vibration.