To prevent the collapse of doup tissues disposed at both the ends of a woven fabric.

In this doup tissue collapse-preventing device in a loom in which doup yarns are opened with an opening mechanism separately disposed from a warp-opening mechanism to form doup tissues at both the side ends of a woven fabric, a control member which is brought into the doup yarns to control the opening of the doup yarns between a reed and the opening mechanism for the doup yarns. The control member has a yarn control member for being brought into contact with the doup yarns to control the opening of the doup yarns, and the doup yarn control member can be adjusted at least in one direction among the vertical direction and the longitudinal direction. The longitudinal direction is the warp direction.