Electrochemical formation of iron nitride thin film has been achieved in a LiCl-KCl-Li3N system at 723 K. When an iron electrode is anodically polarized in the melt, electrochemical implantation of nitrogen proceeds according to the reaction steps: N3- = N-ads + 3e(-) xN + Fe = FeNx Anodically produced nitrogen atoms react with the outermost surface of electrode and diffuse into bulk of iron electrode to form iron nitride thin him. The main phase of obtained nitride layer was found to be an fee-structured gamma'-Fe4N from XRD analysis. From XPS and EPMA results, it was confirmed that the nitride film was composed of a stack of two layers: the top layer was a epsilon-Fe2N1-x layer with a concentration gradient, and the other one was a homogeneous gamma'-Fe4N layer. It is shown that nitrogen concentration in the film and its thickness can be controlled by electrolytic conditions.