PURPOSE: To keep the tension and elongation of an expandable yarn uniform by positively sending out the expandable yarn by press-attaching a rotary friction roller onto an expandable yarn package and setting the taking-up speed of the jointed yarn for the feeding speed of the expandable yarn within a specific range.

CONSTITUTION: A non-expandable yarn Y1 is unraveled from the first yarn feeding package P1, and after passing through a tenser 10 through guides 8 and 9, said yarn Y1 is introduced onto a guide 13 through a guide 11 and a sensor 12, and joined with an expandable yarn Y2. At this time, a friction roller 4 is revolved through a belt 15 by a motor 14, and the second yarn feeding package P2 is revolved to positively send out the expandable yarn Y2. Further, a friction roller 7 is revolved through a belt 19 by a motor 18, and a taking-up package P3 is revolved to take up a jointed yarn Y3. The peripheral speed ratio of the roller 7 for the roller 4 is set within a range of 2.5W4, and the tension and elongation of the expandable yarn Y2 in the jointed yarn 3 are kept uniform.