PURPOSE: To lessen the clogging phenomenon of a diamond cutter and enable accurate cutting by cutting a hard-to-cut material, together with a dress material, by means of said diamond cutter.

CONSTITUTION: When cutting a hard-to-cut member 7 made of a magnetic material or a ceramic material by means of a metal-bond type diamond cutter 9, a dress member 8 made of an alundum group whetstone which is stuck to the hard-to-cut member 7, is also cut simultaneously. As a result, the hard-to-cut member 7 can be cut by the cutter 9, while dressing the cutter 9 by the dress member 8 to prevent the clogging of the cutter 9, enabling a stable cutting operation for a long time.