PURPOSE: To make the thin application of surface plating of a watch case possible by forming a low-m. p. metallic wall part in one piece to the inside circumferential surface of a high m. p. metallic surface case.

CONSTITUTION: A surface case 1 is made by drawing a blank material of superior surface gloss such as stainless steel by a drawing press machine. Next, the case 1 is inserted into die casting dies, and melt of zinc, copper or the like of a low m. p. is poured into this mold a wall part 2. The shape of the part 2 is such that various structures facilitating the mounting of watch mechanism parts to be fitted are provided in one piece. This has the effect of making the case 1 thin and permitting molding of a sharp surface.