A pair of links hangingly support a bearing plate that secures a winding shaft of a shutter curtain. The links are arranged so that the dimension of the space accommodating the links can be minimized. A first link pivots at one end to an end of the bearing plate, adjacent to a shutter guide, and swings at the base end to a side wall of the shutter case so as to project upward away from the shutter guide. A second link pivots at one end to the other end of the bearing plate, away from the shutter guide, and swings at the base end to a portion of the side wall of the shutter case so that the second link extends under the winding shaft toward the shutter guide to bypass the winding shaft. Thus, both the first and second links can be accommodated within the diameter of the winding wheel.