A reversible window is disclosed, which can be reversed by rotation in such a manner that the outer side of the window comes to the inner side thereof, and in which a reverse rotation shaft (17), attached near the central portion of the upper surface of an upper window frame (12) of a window (1), is disposed so as to be slidable, and at the time of the 90-degree opening of the window (1), the window (1) can be moved up to the extreme end of its outer frame.