|The purpose of this study is to derive optimal process conditions of plasma-sprayed chromium oxide coating by design of experiments. Plasma coatings are influenced by various process parameters. According to these process parameters, the quality of the coating layer, that is, the density, the porosity, and the content of the oxide, etc. are changed. In the present study, a statistical approach, that is, design of experiments utilizing L9 orthogonal array table, was used as a method for deriving optimal process conditions. Among the many control parameters affecting the quality of the coating layer, the spray distance, the argon flow rate, the powder feed rate, and the surface velocity were selected as control parameters. A hardness test was conducted on the coating specimens fabricated based on design of experiments and analysis of variance was carried out. As a result, the parameter which has the greatest influence on the hardness of the coating layer is the spray distance, the influence of the argon flow rate and the powder feed rate were insignificant. Optimal process conditions were derived based on the results of this analysis of variance.