To perform precise polishing work by simple operation by performing the polishing work by automatically driving a servo mechanism on the basis of a signal from a control means by previously inputting a polishing condition parameter.

A core thickness and a distance to move a sensor to the drill end are calculated by an operation means on the basis of an inputted drill diameter, and a grinding wheel moving means 2 is driven on the basis of its calculated value, and the sensor is moved to the drill end. When a cutting edge is detected by the sensor, the core thickness is calculated from the inputted drill diameter and the core thickness ratio, and a drill is rotated by a chuck rotating means 4, and the cutting edge is corrected to a horizontal position. A chuck tilting means 5 is driven on the basis of an inputted relief angle, and a chuck is tilted, and the drill is moved by a polishing margin by a chuck moving means 6 on the basis of an inputted polishing margin, and a flank of the drill cutting edge is polished.