To carry out a stable weft insertion while reducing energy required for weft insertion, by making the relation between the delivery speed of a weft from a roller and the transportation velocity by a jet fluid not interfere weft inserting even in the case of changing transportation velocity by a jet fluid.

In this weft inserting apparatus 2 for a fluid jet type loom 1 which is equipped with a roller 13 for frictionally holding a weft Y drawn out from a yarn supplying body on an upstream side apart from a weft inserting nozzle 5, a servo motor 14 for driving the roller, a control means 15 for controlling the servo motor 14 during the weft inserting period according to a fixed velocity pattern corresponding to the rotation angle of a main shaft 17 of a weaving machine and sends a weft for one pick amount from the roller to the weft inserting nozzle, the apparatus is equipped with a tension detecting means 19 for discovering the tension of the weft between the roller and the weft inserting nozzle and a correcting means for calculating the correction amount of the velocity pattern based on the detected value from the tension detecting means and outputting the correction amount.