The confirmation of the volume of the improved body formed by chemical grouting method is usually performed using the uniaxial compressive strength. However, because the target strength of the improved body is not so high, it is difficult to evaluate the difference in strength before and after the improvement. Therefore, it is required to introduce another indicator representing the difference before and after the improvement more sensitively instead of uniaxial compressive strength. In this study, we focused on the change in resistivity before and after the improvement. In this paper, we report the results of small soil tank experiments and field demonstration experiments conducted in order to clarify the electrical resistivity characteristics of improved sand and the scope of application by the proposed method.