Abstract: A device for operating a roll-screen having a winding roll for winding up a screen cloth thereon, which comprises a changeover wheel and a guide wheel in confronting relation with each other, one of which is rotated with the winding roll in screen raising and lowering directions and the other of which is rotated with the winding roll only in the screen lowering direction, the wheels being so arranged that when the screen cloth is lowered two wheels are rotated together, when the screen cloth is stopped and subjected to screen raising force the one wheel is not rotated in screen raising direction due to engagement thereof with the other wheel, and when the roll is slightly rotated in screen lowering direction the one wheel is released from the other wheel whereby the one wheel is freely rotated to make the winding roll wind up the screen cloth thereon.