To improve the design characteristics of outside appearance and to prevent flawing of product bodies while maintaining the high strength of plated parts plated on their surfaces.

A cap member 19 is provided with a first part body 90 of a flexible synthetic resin, such as an elastomer, a second part body 91 made of an acrylonitrile-butadiene-styrene resin disposed on the surface layer side of the body 90, and a plating layer 92 formed by a plating treatment on the surface layer side of the body 91. The base end of a threaded member 18 made of metal is insert-molded in the central part of the body 90. The body 91 is attachably and detachably fitted by elastic locking to the body 90.