To provide a rotary drum type weft yarn-pooling device of a loom and weft yarn-feeding device of rapiers loom, capable of performing the non-twisted insertion of a plane string, multifilament having a flat cross section such as a carbon fiber, glass fiber, etc., and a flat yarn such as a tape yarn, etc., and also capable of performing a high speed weaving as compared with those of the conventional structures.

This yarn-pooling drum 21 is accelerated/decelerated or stopped its rotation so that the wound amount of the weft yarn on the yarn-pooling drum becomes as a constant amount or the delivering position (loosening position) 40 of the weft yarn from the yarn-pooling drum 21 becomes as constant even on performing the weft insertion. Also on the yarn-pooling drum 21 accelerated/decelerated or stopped its rotation, the flat yarn 29 drawn out from wound body 1 of the weft yarn such as a bobbin is wound tidily in non-twisted state.