Railroad structures must be installed at a sufficient distance from trains based on the railroad's structure gauge. Consequently, there is a demand for a system that can accurately and efficiently determine the positions of these structures. We have developed a system that uses a single 2D-LiDAR to measure structures such as tunnels inside a railroad and to generate accurate 2D drawings. However, it was not possible to clearly distinguish which structure the measured points on the 2D drawing indicated, so visual confirmation was required. In this study, we propose a material identification method that is based on the incidence angle of the laser light in 2D-LiDAR to identify the type of structure on the generated 2D drawing. The accuracy of the system, when using the proposed method, was evaluated by the identification rate and the error in the calculated incidence angle. Verification experiments demonstrated that the identification accuracy exceeds 90%, and particularly high accuracy was observed for certain materials. The results of this research are of great importance in maintaining and managing railroad infrastructure.