PURPOSE: To easily regrind a drill edge point by aligning the drill edge point onto the internal periphery of a cup grindstone while setting the center of a drill to a part spacing an arbitrary distance from the center line of this grindstone and moving the drill in its edge point linear direction.

CONSTITUTION: The center of a drill 1 is set to a position lowered by an arbitrary distance L from the rotary center line A of a cup grindstone 2. Next moving the drill 1 in a linear direction X-X' of its edge point 3 in a manner wherein the edge point 3 of the drill 1 is adapted to a point Q on an internal periphery B of the cup grindstone 2, an arm relieving clearance 4 along the internal periphery B of the cup grindstone is successively ground from the center part of the edge point 3.