The present invention is to provide a method and device for polishing a glass substrate, suitable for polishing a large-sized glass substrate. The device for polishing a substrate is adapted so that a substrate is attached to a film stretched on a frame; the frame is installed on a carrier; the carrier and a polishing surface-plate are brought closer relative to each other to polish a surface to be polished of the substrate attached to the film by pressing the substrate to the polishing surface-plate; the frame is removed from the carrier after the completion of the polishing, and the polished substrate is removed from the frame.