INSPECTING METHOD OF CYLINDRICAL OBJECT

PURPOSE:To provide a cylindrical object inspecting method which evaluates dirt or the like of the object with high accuracy irrespective of the color of the material of a piston skirt part of the piston, and also achieves shortening of the evaluating time and quantifying of the evaluating result, saving of labor, etc. CONSTITUTION:This is an inspecting method of a cylindrical object to evaluate the state of dirt or the like at an outer peripheral part of the cylindrical object based on the images of the object. The inspecting method includes a first inspecting process wherein three factors of a standard color are operated on the basis of a color system. Moreover, the inspecting method has a second inspecting process wherein a to-be-processed image is retrieved from the images of the cylindrical object, and a third inspecting process in which the three factors of the standard color are compared with those of the color of the to-be- processed image. The inspecting method consists of the above first-third processes and a fourth inspecting process wherein the dirt or the like at the outer peripheral part of the cylindrical object is evaluated on the basis of the comparison result.