PURPOSE: To enable improvement in weft feeding efficiency with prevented occurrence of yarn breakage by operating a positive feeding mechanism during a period from start of picking to a time of unwinding a prescribed amount of weft before completion timing and positively feeding an accurate length of yarn.

CONSTITUTION: An enging pin 7 is retreated with a controller 14 at a rotation angle corresponding to timing of picking start. Weft 2 in a stored state is then unwound from the outer periphery of a fixed drum 6 and an operation command is simultaneously sent to a rotation controller 15 after a prescribed time lag to drive a feed plunger 21. A roller 18 in a standby position is subsequently brought into contact with a roller 17 to nip the weft 2, which is then positively pulled out from the outer periphery of the drum 6 through the rotation of a servo motor 16 and delivered to a main nozzle 9. The plunger 21 is returned with the controller 14 on a sensed signal of a sensor 13, indicating the unwinding of the prescribed amount of the weft. The rollers 17 and 18 are separated to stop the operation of the positive feeding mechanism 12. The rotational speed of the serve motor 16 at this time is sufficiently lowered without causing a rapid change of tension in the weft 2.