PURPOSE: To prevent reverse winding on a feed roller with increased thread switching efficiency by forming circular grooves for engaging and retaining threads around a guide bar at positions where threads contact and pass through when switching the threads, and by rotatably supporting and rotating the guide bar in the thread running direction.

CONSTITUTION: Guide bars 8 and 8' with thread engagement-retaining grooves 12's circularly cut at positions where threads contact and pass through when switching the threads are rotatably supported at a supporting end 22 with a fixed boss 23 and a rolling bearing 24. The guide bars 8 and 8', while being rotated by threads contacting and running on their surfaces when there is no rotary drive source, can also be positively rotated in the direction in which threads are bent and run by jointly employing a motor shaft 26 and a coupling 27 at the supporting end 22. Accordingly, reverse winding on the feed roller during thread switching can be prevented even when threads vulnerable to friction resistance due to guides and others and wound with improved thread switching efficiency and stabilized winding.