PURPOSE: To provide grinding work with the same high accuracy as preceding work even after dressing or truing by carrying out a series of combined work including grinding work with a workpiece attached only one time.

CONSTITUTION: With a grinding wheel 343a attached onto a tool head, the grinding wheel 343a is dressed by a dressing means 302 by relatively-moving the dressing means 302 so as to bring it into contact with the grinding wheel 343a by means of drive systems 12, 13. By relatively-moving a grinding wheel measuring means 303 so as to bring it into contact with the grinding wheel 343a by means of the drive systems 12, 13, the dimension of the grinding wheel 343a is measured by the grinding wheel measuring means 303. It is thus possible to carry out a series of combined work including grinding work with a workpiece attached only one time, dress or true the grinding wheel 343a, and maintain high processing accuracy.