PURPOSE: To eliminate damage of a tool at the time of making the sharp diamond tool on a workpiece and to shorten dead time by the time when the tool is made contact with the workpiece.

CONSTITUTION: This device is constituted of a photo diode 16 which is a means to optically measure a clearance between the addendum of a tool 4 and a workpiece 3, a load detector 5 which is a means to detect that the tool 4 makes contact with the workpiece 3, a coarsely moving table 7 which is a coarsely moving drive means to bring the tool 4 close to the workpiece 3 and a laminated type piezoelectric actuator which is a fine drive means.