WEFT INSERTION DEVICE FOR RAPIER LOOM

A weft insertion device (1) includes a yarn guide mechanism (50) that includes a holding device (51) including a holding body that is disposed below the movement path (P) and holds a flat yarn (Y), a guide device (55) that is disposed above the holding device (51) and guides a tip portion of the flat yarn (Y) to the holding device (51), and a guide member (53) that guides the flat yarn (Y) at a position above the movement path (P). The guide device (55) includes a guide plate (55a) that is disposed directly above the holding body so as to be perpendicular to a weaving width direction and a guide-plate driving device (55g) that displaces the guide plate (55a) between an upper standby position above the movement path (P) and a guide position where an end of the guide plate (55a) reaches the holding body.