PURPOSE: To enable the setting of the elongation difference between the constituent filaments in a mixed yarn to a definite level while arbitrarily selecting the denier of each single filament, by extruding a molten polymer through the nozzle of a conventional spinneret and through a nozzle having a needle placed at the center of the nozzle hole and protruded beyond the surface of the spinneret, and taking off the extruded filaments at the same take-up speed.

CONSTITUTION: A molten polymer is extruded through the nozzle 3 of a conventional spinneret and through a nozzle having a needle 7 inserted into said nozzle, and the extruded filaments are taken up at the same take-up speed. The elongation of the filament extruded through the nozzle having the needle is lower than that of the filament extruded through the ordinary nozzle, and the dyeability of the former filament is improved when compared at the same elongation. The elongation is increased by decreasing the protruded length of the needle and is decreased by increasing the length.