PURPOSE: To continuously mold a receiving mouth at the end part of a synthetic resin pipe member.

CONSTITUTION: A heating device 4 is arranged on one side of a clamp device 1 and a receiving mouth molding machine 6 is arranged on the other side thereof. The end part of the synthetic resin pipe member P clamped by a clamp device 1 is heated and softened by the heating device 4 and, subsequently, the clamp device 1 is rotated by 180° on a horizontal surface to insert the core mold 61 of the receiving mouth molding machine 6 in the heated and softened end part of the pipe member P to mold an expanded receiving mouth. By this constitution, the receiving mouth can be efficiently and continuously molded at the end part of the synthetic resin pipe member P.