a cleaning apparatus according to the present invention is provided with a brush drive mechanism which brings a brush being rotating closer to a substrate , measures electrical potentials generated on a plurality of conductor patterns formed on the substrate , by a contact and separation with / from tips of scrub materials of the brush being rotating , and controls a positioning of the brush by use of the measurement results . with the process as described above , it is possible to treat uniformly a surface to - be - cleaned for a large - sized substrate , with the cleaning brush . consequently , it is possible to form a highly qualified transistor for liquid crystal display on the substrate having been cleaned , with enhancing yield .