PURPOSE: To heat-set only a desired part through the intermediary of a heating material by providing a high-frequency induction heating body in the intermediate part of a pipe material of a thermoplastic synthetic resin pipe and by heating only the desired part.

CONSTITUTION: A pipe body 1 is formed of a thermoplastic synthetic resin material and a heating layer 2 is molded in a state wherein a material 21 having the same quality as the molding material of the pipe body l and a powder-grain substance 22 formed of a heating material are kneaded. The heating layer 2 is provided in the intermediate part of the pipe body 1 and moreover to be cylindrical at over the full length in the longitudinal direction of the pipe body. In addition, the heating layer 2 is molded integrally in the pipe 1. By applying high-frequency waves of high-frequency emitters E to parts N of a pipe 10 to be bent, the heating layer at these parts is heated to be softened. The pipe thus prepared is pressed in a mold M so that a crank type is formed, only the bent parts N of the pipe 10 are cooled down thereafter and thereby a crank- type pipe is obtained.