This paper describes the elucidation about the surface modification processing of permalloy 45 using Na2SO4-electrolyzed oxidizing water (It abbreviates as Na2SO4 EO water). Firstly, as for the influence of Na2SO4 EO water on the surface micro shape of permalloy 45 which was processed in the polish to the mirror surface, it was made clear using the results of FE-SEM observation and AFM measurement of the test pieces surface before and after immersion processing. The results is as follows. In the case of non-heating processing, if using Na2SO4 EO water compared with the H2SO4 solution and NaCl EO water, the test pieces surface is more uniformly done by the etching. In the case of heating processing, Na2SO4 EO water, H2SO4 solution and NaCl EO water are same and don't have big influence on the test pieces surface. Next, it reviewed about the removal of surface oxidation layer in the test pieces surface after heating processing. The results showed the surface oxidation layer can be more efficiently removed if using Na2SO4 EO water compared with H2SO4 solution; however, there is possibility that surface oxidation layer which is thicker than a natural-oxidation layer is formed. By this study, it got the possibility that Na2SO4 EO water can be applied to the surface modification processing of permalloy 45.