Over the last several decades, many concrete tunnels have been constructed on roads, highways, and railways. For safety in concrete tunnels, periodic inspections have been conducted using nondestructive testing technologies and techniques. However, non-destructive test cannot replace the visual inspection due to their slow and complicated procedures. For this reason, they have been limited to precision inspections. The visual means also need time and there may be subjective in the measured crack data. Here, this study proposes inspection system for fast measuring cracks in tunnel lining and providing objective crack data for safety assessment. The system consists of both image data acquisition system and analysis system. The acquisition system takes images with CCD line-scan cameras. The analysis system extracts crack information from the acquired images using image processing. Measured crack information is crack thickness, length, and orientation. To improve the accuracy of crack recognition, the geometric properties and patterns of cracks in concrete structure should be applied to image processing. This proposed system was verified through a series of experiments in both laboratory and field environment - subway tunnel.