PURPOSE: To prevent happening of a fault in a selvage structure caused by an inaccurate gripping operation of a gripper due to accumulation of waste fibers, in relation to a method for forming a tuck-in selvage in a shuttleless loom and a device therefor.

CONSTITUTION: When moving a needle 12 nipping the end of a weft yarn backward and drawing the weft yarn out of a gripper 20 while bending back the end 49 of the weft yarn into the shed of warp yarns, the gripper 20 is slightly opened. The gripper 20 is attached to a shaking bracket 19 pivoted to a stationary bracket 15 fixed to the second mobile unit 2 in a state where the gripper is energized by a spring 31 in the closing direction. A control unit 30 for making this gripper 20 perform an opening operation is also attached to the shaking bracket. A back-up piece 32 is attached to the control unit 30 and a shaking unit 42 connected to the stationary bracket 15 at one end and facing to the back-up piece 32 at the other end is pivoted to the first mobile unit 1 set adjacently to the second mobile unit 2. The other end of the shaking unit 42 is brought into contact with the back-up piece 32 by a relative motion of the first mobile unit 1 and the second mobile unit 2 so as to push the control unit 30 in the direction for opening the gripper.