Quality of products and reduction of products inspection burden are required in production. This paper describes development of automatic inspection system for cylindrical products by image processing. Since a cylindrical product is an axisymmetric object, the scratch can be detected by image processing on the difference image of the captured images. Based on this idea, we have developed the scratch detection algorithm. It has the threshold setting method where the threshold adjustment is able to be done easily by considering the threshold as image data. The availability of the developed inspection system is shown in the experimental result where actual inspection was carried out on a large quantity of cylindrical products.