An optical system includes an optical element and an imaging device. The optical element has a surface on which a plurality of sub-wavelength structure bodies are formed. The imaging device has an imaging region which senses light via the optical element. The surface of the optical element has one or two or more sections that scatter incident light and generate scattered light. A sum total of components of the scattered light reaching the imaging region is smaller than a sum total of components thereof reaching regions other than the imaging region.