An apparatus for matting a coating applied on mainly flat panels includes a cleaning workstation and an excimer treatment workstation where the panels are conveyed by a belt conveyor having an upper outward section and a lower return section. In the cleaning workstation, the upper outward section of the belt conveyor has a V-shaped path, which is formed by two rollers in contact with the plane of advancement of the panel, and a roller in lower position, and which is bridged by advancing rollers, among which gaseous nitrogen is supplied that brushes all sides of the panel. In the treatment workstation, the upper outward section of the belt has a V-shaped path, where the panel is irradiated by an excimer emitter, and which is formed by two rollers in contact with the plane of advancement of the panel, and a roller in lower position, and is bridged by advancing rollers.