To perform the setting of the most advanced position of a rapier head in a weft insertion device of a rapier loom efficiently.

This weft insertion device 1 of the rapier loom in a type of performing a delivery of a weft yarn 2 from a rapier head 5 for conveyance for holding the weft yarn 2 from one side and progressing into an opening 4 of warp yarns 3 to a rapier head 6 for receiving for progressing into the opening 4 of the warp yarns 3 from the another side, is provided with standard marks 15 and 16 for setting the most advanced position of the rapier heads 5 and 6 in the vicinity of a traveling passage of the rapier head 5 for conveyance and the rapier head 6 for receiving or members 7, 8, and 31 linked with the rapier heads 5 and 6, and setting the most advanced positions of these rapier heads 5 and 6 easily and accurately by adjusting the rapier head 5 for conveyance and the rapier head 6 for receiving at the standard marks 15 and 16 for making the multiplying amount of the both rapier heads 5 and 6 as an adequate amount.