PURPOSE: To grind a tool cutting edge with high precision, by a method wherein a control means to control relative position between the cutting edge of a cutting tool held by a holding part and a grinding tray is provided, a measuring device to measure the shape precision of the cutting edge to be polished is situated on a machine, and unevenness in polishing efficiency is suppressed.

CONSTITUTION: In order to suppress deterioration of cutting edge shape precision due to difference in polishing efficiency due to anisotropy of a diamond impeding cutting edge shape precision, the cutting edge of a diamond bite 3 is forcibly pressed against a polishing tray 1a in a first process. Through rotation rocking of a hold arm 4, a relative position between a diamond and a polishing tray 1a is controlled, and through integration of a plurality of fine polishing planes, a molding work is applied on the cutting edge to form a polygonal shape similar to an arc of a circle. The shape of the cutting edge is measured by a measuring device 9 on a machine, a polishing amount of the fine polishing surface is grasped, and based on the measurement, the similar polygonal shape is corrected to a similar shape to that of an arc of a circle with high precision. Thereafter, the cutting edge is formed in the arcuate shape of a round by means of a polishing tray 1b.