It is now practical to use continuously scanned images (CSI), taken by a line sensor camera, for inspection of railway facilities. Such inspection system has been under development since 1995. Railway facilities are so extensive that this system will provide an effective tool of taking those images. In this paper, we report the result of its application as an inspection system of tunnel wall deformation. Especially, we focus on the image processing technique to extract those deformations. We completed an original image processing database system and a graphical user interface for convenient and easy operation. This system enables us to diagnose the soundness and durability of tunnel wall at a higher accuracy level.