Abstract: In a wristwatch case, a nonmetal dial plate (305) is disposed so as to face a transparent window plate (304), and a movement (303) with a built-in antenna is disposed between the nonmetal dial plate (305) and a nonmetal back cover plate (306). A metal annular window frame (301) and/or a metal annular back cover frame (302) has an extension (L1, L2) extending appropriately toward a metal annular base (300). Thereby, in the wristwatch case, the outer periphery of the movement (303) with a built-in antenna disposed between the nonmetal dial plate (305) and the nonmetal back cover plate (306) is surrounded so that the region is divided vertically, by the metal annular base (300) and the extension (L1) of the metal annular window frame (301) and/or the extension (L2) of the metal annular back cover frame (302).