Radioluminography is a new type autoradiography, in which a radioactivity distribution pattern is recorded in a photo-stimurable phosphor layer of an imaging plate, then converted, on a reading unit, to digitalized image data storable in a disk, and finally visualized and quantitatively analyzed by using an analyzing unit. This method was applied to the evaluations of ⁵⁹Fe and ⁶⁴Cu adsorption on Si wafer surface and of SC-1 (NH₄OH : H₂O₂ : H₂O=1 vol : 1 vol : 5 vol) cleaning efficiency against these adsorbed impurities. The distributions of the adsorbed radioisotopes before and after the cleaning were manifested to be understood at a glance. It was found that radioisotope density in any area at any position on the wafer could be determined with the detection limit of the order of 10⁸ atoms/cm² and the dynamic range over the order of 10⁴.