Provided is a structural birefringence-type inorganic wave plate having excellent heat resistance and durability, and a fine pattern. Also provided is a manufacturing method for an inorganic wave plate by which, even in the case of a fine pattern, productivity is high, and a desired phase difference is easily achieved and stably obtained. This inorganic wave plate is obtained by utilizing a selective interaction between a polymer having a repeating unit containing a carbonyl group, and a metallic oxide precursor, the inorganic wave plate having a wire grid structure provided with a transparent substrate, and grid-shaped protruding portions arranged at a pitch shorter than the wavelength of light in a used band on at least one surface of the transparent substrate and extending in a predetermined direction, the main component of the grid-shaped protruding portion being a metallic oxide.