An antireflection film substrate that is provided on a surface of a substrate includes a surface layer having an alumina hydrate as a main component. The surface layer has an uneven structure in which a volume proportion of the alumina hydrate per unit volume decreases in a direction from the substrate side to a surface side, and a period of apexes distributed on the uneven structure on the surface side is configured to be equal to or less than a wavelength of light of which reflection is to be suppressed.