PURPOSE: To surely distinguish the nonconforming contents of a drill edge and facilitate the automation of inspection by comparing a reference value formed from a cutting edge width data and a drill-diameter/chisel-angle data with a value obtained from a drill edge data to judge the conforming and nonconforming of the drill edge.

CONSTITUTION: The chart of a cutting edge is obtained by processing an image taken by a photographing device and formed by the processing of the coordinate transformation of infliction points and linear interporation, etc., and, from the figure, the coordinates of infliction points A-G and the inclination Q1-Q4 of each section are taken into a processing data table and, then a cutting edge width data are formed using this processing data. Using the cutting edge width data and previously inputted drill diameter data and chisel width data, a theoretical data is formed and housed in the table, and the processing based on a previously taken-in drill edge data is compared with this theoretical data. The contents of comparison are the three components of R, S, T as shown by the chart and when the values thereof exist within a defined range between the processing data and the theoretical data, it is judged conforming, and its allowable range can be previously set by a parameter.