To enable a stopper to be smoothly passed into a through hole when the stopper is attached to a cord at the same time that it is injection-molded from a synthetic resin and when a molding taken out of a die is split into two stoppers attached to the end of the cord, without forming projections at its cut portion, and to enable working efficiency to be enhanced by enabling the cutting operation to be performed on an assembly line subsequent to the molding operation.

A cord 4 is passed into a die hole 6 in a die 7, and a bar-shaped stopper made of a synthetic resin long enough to project from the cord width is provided on the outer periphery of the cord 4 by die molding it. In this case, the die hole 6 is one cavity 8 of a cross section such that two dumplings are aligned where approximately elliptical cavities 8 at a portion to be formed into the bar-shaped stopper are provided in connection with each other and a narrow communicating portion 9 is provided at their connection; after the synthetic resin is injection molded inside the die hole 6, a narrow part formed by the communicating portion 9 in the synthetic resin molding formed by the die hole 6 is cut along with the inner cord 4 into two stoppers made of the synthetic resin which incorporate the end of the cord 4.