PURPOSE: To provide a glass washing device which does not slip downward by its self weight when a washing is performed while laterally moving along the lower frame of a glass, and therefore which does not cause a vacuum break by getting on the lower frame.

CONSTITUTION: A washing robot 2 has washing liquid jetting devices 13, 14 which jet a washing liquid on the surface of a glass G, main suction cups 5, 6 which detachably stick to the surface of the glass G and move in the lateral direction, and subsidiary suction cups 7, 8 which move in the vertical direction, and can move either in the vertical or lateral direction while washing the surface of the glass G. The washing robot 2 is supported by a supporting device 3 which is provided above, and the operation of which is controlled by a control device 4. Under the main suction cups 5, 6, rollers 15 to prevent a downward slipping from happening, which are put on a caulking member C of a lower frame A of he glass G to be washed, and can move in the lateral direction while supporting the washing robot 2 upward, are provided. By this method, the main suction cups 5, 6 do not slip downward by the self weight of the device, and do not cause a vacuum break by getting on the lower frame A.