PURPOSE: To provide the economical labor-saving thread fastening structure of an outside plate such as FRP in which an outside plate such as FRP can be thread-fastened to a frame quickly and surely, without revising a fitting hole even if a little dislocation is generated between the fitting hole of the outside plate such as FRP and the fitting hole of the frame.

CONSTITUTION: In the constructtion in which an outside plate such as FRP, plastics, glass, ceramics, and sheet steel is thread-fastened to the fitting hole of a mating frame through its fitting hole, the following are provided: the fitting hole of the outside plate larger than the fitting hole 10 of the frame 1, a fixed sleeve 3 to be fitted to the fitting hole of large diameter and having a center hole of relative large diameter, and a blank flange part 13 coaxially projectingly provided on the upper end of a cylinder part rotationally movably inserted in the center hole of the fixed sleeve 3. The blank flange part 13 is provided with a movable sleeve 4 having a relatively long slot hole extending in the diametral direction and of width allowing insertion of the bolt, and a slip-out preventing stopper projectingly provided on the lower end of the movable sleeve 4.