To enable sequential winding of an elevating cord without overlapping, and its smooth unreel.

The winding device comprises a rotary shaft, a threaded rod supported irrotationally to the rotary shaft and able to rotate normally and reversely together with the rotary shaft, and an elevating cord winding rod which is continued from an end of the threaded rod, supported irrotationally to the rotary shaft and able to rotate normally and reversely together with the rotary shaft. An end of the elevating cord is connected to the other end of the elevating cord winding rod. The winding device further comprises an elevating cord guide mechanism including a guide block and a guide member. The guide block has a through hole having a female screw in right and left directions by which the guide block is externally fitted to the threaded rod in an engaging manner. The guide block is fitted to a rail to be locked by the rail so that it may not rotate together with the threaded rod. The guide member extends from the lower side of the guide block toward the elevating cord winding rod in parallel thereto, and has a guide hole in the extended end part so that the end of the elevating cord may pass through it to be guided.