To improve rigidity with a thinner wall and a lighter weight than those of a casing obtained by a single resin molded product without using a reinforced resin material or metal material filled with glass fiber, carbon fiber or the like.

This casing is used for an application required for a thickness of a predetermined value or more at the time of constituting by only a first material. In this case, the casing comprises a base material 1 made of the first material, a first metal plated layer 2 laminated on the material 1, and a second metal plated layer 3. The casing is thinner and lighter and those of that constituted by only the first material with rigidity equivalent or more thereto.