To solve the problems in the tucking of a weft into a weft detector or the like immediately after insertion without interfering the insertion of the weft, comprising irregular insertion, and inaccurate detection and checking to cause weft-stop, weft breakage, or the like of a jet loom.

The weft tucking device includes an arm 4 suspended from or standing on at the upper part of the side of a cloth fell 19 of a reed 3 in a manner swingable in the direction same as the beating direction, swinging forward to the cloth fell side 19 beyond the reed 3 by the inertia of the beating motion and tucking a just-inserted weft 2 into a hook part 7a of a weft detector 7 or a weft engaging hook placed separately from the weft detector 7, a stopper 5 to restrict the forward motion limit of the arm 4, and a weight 8 attached to the tip end of the arm and energizing the arm 4 in the retreating direction to retreat to the side of the reed 3 from the insertion path of the weft 2 in the insertion of the weft 2. The inertia force to tuck the weft 2 can be increased to surely tuck the weft 2 into the hook part 7a by changing the weight of the weight 8 according to the thickness of the yarn. The accuracy of weft detection is improved by attaching an iron piece and a sensor to the arm 4.