We proposed a new synthesis route; combination of nitriding and de-nitriding method as a new process for the formation of ordered L1(0)-FeNi. Firstly, electrochemical nitriding was investigated in LiCl-KCl-CsCl-Li3N system and a single phase of FeNiN was obtained by potentiostatic electrolysis at 1.8 V. Furthermore, de-nitriding was also investigated in LiCl-KCl-CsCl system at 573 K. From the result of XRD, obtained sample was identified as L10-FeNi and the order parameter was determined to be 0.71. We achieved the world's first the formation of FeNi which has superlattice structure by electrochemical method. (c) 2017 The Electrochemical Society. All rights reserved.