To provide epoch-making technology for turning a cutting edge of a circular chip with high rotation accuracy to obtain good finished surface roughness and manufacturing technology of a shank capable of easily and efficiently replacing the circular chip to attain the high rotation accuracy of the cutting edge.

A cutting method includes: a step of inserting and fixing the circular chip to an installation rotary shaft provided on a circular chip holding part at the tip of the shank for use in a motorized forcible driving rotary cutter (DRCT); a cutting step of cutting a flank of the circular chip using another grinder different from the cutter by a rotary whetstone to reduce deflection of the cutting edge of the circular chip while turning the circular chip as an object to be cut after it is inserted and fixed; and a step of cutting a workpiece using the circular chip worked on the flank while it is kept inserted and fixed to the installation rotary shaft. A chip holder of an assembly shank is preferably used, which is three-divided into the chip holder for holding the circular chip, the shank body and a connecting holder for coupling the chip holder with the shank body or two-divided into the chip holder for holding the circular chip and the shank body.