The purpose of this study is to investigate the conditions of fabrication of cellulose nano-fiber (CNF) composited Ni plating film by electroplating method and clarifying the codeposition mechanism. The electroplating was carried out on SUS304H using Watts bath with CNF suspended. The obtained films were evaluated by surface and cross-sectional observation including elemental mapping analysis, X-ray fluorescence analysis and Vickers hardness testing. The obtained film had a double layer structure parallel to the plating surface, and the layer on the substrate side contained a large amount of CNF. This layer is considered to be formed by physical trapping of CNF in the pitting corrosion and the delaminated area inside the substrate caused by the effect of chloride ion and hydrogen gas. It was also suggested that the electrostatic repulsion between CNF and the substrate was one of the factors that resulted in little CNF codeposition within the surface side layer. In addition, the Vickers hardness of the surface was improved by approximately 30% compared to electroplated Ni film without CNF.