To provide a decorative cap assembly which can be easily mounted or removed without affected by material quality of a decorative cap and can improve appearance and design.

The decorative cap assembly is equipped with a fastening member having a shaft part in a cylinder shape or a conical shape and a head part 4a, formed at an end of the shaft part, of which diameter is longer than the diameter of the shaft part, the decorative cap 1 formed so as to cover the head part and a ring-shape member 2. An inner peripheral surface of the decorative cap 1 is formed as a female screw. An outer peripheral surface of the ring-shape member 2 is formed as a male screw for mating with the female screw. The ring-shape member 2 is formed to encompass the head part with the decorative cap 1 by screwing the male screw into the female screw.