Nitrogen is well known as a beneficial alloying element which entitles stainless steels an enhanced corrosion resistance against chloride attack. The introduction of N into the surface of stainless steel can be achieved by electrochemical nitriding. The role that Nitrogen plays in pitting resistance has long been discussed focusing on the distribution and incorporation form of N as well as the modification to the local corrosive circumstance induced by the N-participated electrode reactions. For electrochemical nitriding, stainless steel surface, as the place on which involved electrode reactions occur, is expected to undergo structural evolution. This, to some extent, would influence the corrosion property of nitrided stainless steel. Detecting the structural evolution occurring in the electrochemical nitriding is of great significance for deciphering the involved electrode reactions and thus optimizing the nitriding parameters. In this work, using atomic force microscopy as well as transmission electron microscopy, we have clarified the concomitant localized reductive dissolution of passive film, anodic dissolution of metal matrix at micro-anodic sites, as well as re-deposition of the dissolved metal cations, which roughens the surface by forming the undulations at surface with undulation amplitude in the range of a few tens of nanometers. Element mapping analysis by Super EDS technique reveals that the re-deposited product is mainly comprised of iron oxide, which indicates iron is dissolved and the resultant iron cations occurs re-deposition.