The wear tests under light load were carried out for some kind of radical nitrided SKD61 and ion nitrided one, in order to investigate the properties of wear and friction. In the case of ion nitriding and radical nitriding increased the ration containing NH_3,compound layer was observed. Surface layer was highly hardness by nitriding, and the hardness were almost the same in all cases. As a result, resistance to wear was highly improved by radical nitriding. Its degree was about 1% to quench and tenpered one, and one half to ion nitrided one. These results may be caused by the formation of compound layer.