The folding window is mainly composed of door frame, window sash, transmission parts, rotating arm parts, transmission rod, directional device, etc. The frame of one side of the side window sash is connected to the middle window sash by a hinge. The upper and lower ends of the window sash on the other side of the folding window side sash are respectively equipped with upper and lower rotating shafts, which are connected to the upper and lower rotating shaft seats of the window frames on both sides of the door opening. The side window sash will rotate around the side sash and drive the middle sash to rotate to 90°, so that the window sash can be opened and closed. The folding window is a window with foldable sash. When the window is fully opened, the sash is folded and arranged on one or both sides of the opening. Because the rotation radius of the folding window is small, the space in front and behind the door opening can be fully utilized after the window is opened.