The final objective of this study is to develop a diagnosis method for evaluating the corrosion of reinforcement bars in concrete structures using a complex resistivity method that improves the problem of the previously established resistance method. The steel surface resistivity of reinforcement bars is to be estimated in specimens as a basic study of this objective. In the experiment, the four factors, such as water to cement ratio(W/C) that represent corrosion environments, reinforcement diameter, cover depth, and presence of mill scale, were considered. In the analysis of the complex resistivity, a resistivity estimation method (REM) that is able to estimate the concrete resistivity and steel surface resistivity at the concrete surface was used. The results of this study will be applied as basic informations for the evaluation reference in corrosion analyses using a complex resistivity method.