Abstract: The present invention provides a production process of, duplication plate material for duplication of, and medium provided with an optically diffractive structure such as a hologram and diffraction grating having excellent optically diffractive effect, wherein the optically diffractive structure has a surface configuration having plural corrugation-like convexo-concave shapes, and the convexo-concave shapes of the final medium is formed by using a duplication plate material. The convexo-concave shapes of the duplication plate material have a cross-sectional surface which is crosswise to the peaks of the convexo-concave shapes, and a salient section defined by a salient line and a middle line has a smaller area than that of an adjacent reentrant section defined by a reentrant line and the middle line. Herein, the middle line is drawn by connecting midpoints of the height of the convexo-concave shapes.