PURPOSE: To enable rapid and simple correction of a tip cutting edge and to reduce the weight of a device, by a method wherein the holder of a drill is situated to a support part member and a tip cutting edge can be set in parallel to a table, and by steppedly setting the angle of a driven part, the working surface of a grinding stone can be caused to coincide with an escape angle.

CONSTITUTION: A drill 15 is set to a support member 11 after it is secured to a holder 16, and the tip cutting edge of the drill 15 is positioned in parallel to the upper surface of a table 9. The revolving angle of the support member 11 is steppedly set, the one tip cutting edge is positioned in parallel to the working surface of a grinding stone 5, and by steppedly setting the angle of a motor 4, the working surface of the grinding stone 5 is caused to coincide with the escape angle of the drill 15. With this state, by rotating the grinding stone 5, the table 9 is moved to grind the one tip cutting edge. On completion of grinding, the drill 15 is moved aside, and the holder 16 is rotated in a 180° arc to grind the other tip cutting edge. This constitution enables rapid and simple correction of the tip cutting edge of the drill 15, and reduces the sizes of both the motor 4 and table 9, resulting in the possibility to reduce the size and weight of the device as a whole.