The demand for crazing inspection robot rises to improve work efficiency of the sewer pipe inspection. Since it cracks in the surface in a pipe and a pipe bonding link etc. is in except, there is a problem which a robot incorrect-recognizes. In this research, it cracks using the discrete Haar-wavelet transform, and a candidate is recognized. Furthermore, the bonding link of a pipe is recognized using the Hough conversion, and how to detect a crack is described.