To provide a method for forming an integrated end support body with a seam and a molding line invisible by providing a body part of aerodynamic shape, and a bottom part integrally formed at the body part, and forming the end support body as a single integrally formed part with the body part and bottom part directly fitted to the outer surface of the body.

An end support body 20 is provided with a body part 26 and a bottom part 28. The body part 26 is composed of an end part, a center part and a neck part so as to form the aerodynamic upper side outer surface curved gradually upward in cooperation, thus contributing to the decrease of wind noise. Three molds 54, 56, 58 are moved in the mutual directions to form a molding cavity. After three modes are energized in the mutual directions and brought into mutual contact, fused thermoplastic resin such as fused polyvinyl chloride is injected. Upon the end of injection, a pressurized fluid enerigizes the fused thermoplastic resin to the outside so as to be pressed to the respective inner surface walls of the molds 54, 58 and the inner surface 70 of the second mold 56, and after cooling for the fixed time, the end support body 20 is obtained.