The concrete lump exfoliation phenomenon to line from the Sanyo Shinkansen tunnel which occurred in June, 1999 was taken up as a big social problem about security of the Bullet train. With this, they established the inspection system of the Department of Transportation railroad engineering works structure, and the way of the maintenance of the structure which a railway company should perform has been arranged. On the other hand, in West Japan Railway Company. (following, JR WEST), we wrestled for the elaborate inspection and repair measures of the tunnel cover mechanic not to make any producing serious exfoliation to line again based on the reflection of this phenomenon. In addition, We clarify the tendency of the exfoliation risk by looking back on enormous inspection records and data accumulated in an approach and we consider and carry out the measures that you should perform.