Corrosion of reinforcement is the representative deterioration of concrete structures, and it may cause the reduction in load-carrying capacity. Therefore, protecting reinforcement from corrosion is one of important subjects for concrete structures. Recently, in order to protect reinforcement, use of penetrant type inhibitor is increasing. However, evaluation method of penetration depth of these materials has not been established, and it is difficult to judge whether these materials work well or not. Then in this study, in order to develop the technique to evaluate penetration depth by surface analysis in the future, evaluation of penetration depth and active ingredient amount of 3 penetrant type inhibitors were tried by Raman spectroscopy as a basic study. To evaluate the amount, granular silica was mixed into concrete as a target of Raman spectroscopy analysis, and the amount penetrated into the silica ball was analyzed. Here we found that as the depth from coated surface became deeper, the relative amount of the detected active ingredient becomes smaller. This result indicates that the penetration depth can be predicted by evaluating the near surface by Raman spectroscopy.