To provide a structure by which fine rugged parts of micron order can be formed accurately, and to provide a diffraction grating having the fine rugged parts.

A plurality of the fine projecting parts 2 composed of a material of a kind separate from the material of a substrate 1 and respectively finely spaced from each other are arranged, to project on a surface part of the substrate 1. The fine rugged parts 5, capable of diffracting light, are formed by a plurality of the fine rugged parts 2 and the surface part 1a of the substrate 1 which is the base of the fine spacing. The construction material of the substrate 1 and the construction material of the fine rugged parts are formed of the materials, varying in the etching selection ratio.