PURPOSE: To set the amplitude voltage by detecting the displacement amplitude of XY scanning and Z control with a piezoelectric displacement sensor and to display and set the displacement amplitude by detecting the displacement amplitude of the XY scanning and the Z control with the piezoelectric displacement sensor.

CONSTITUTION: A microcomputer 22 controls an XYZ-driving piezoelectric body 28 in the three-dimensional directions through a Z control part 23, an X control part 24 and a Y control part 25 and transfers the Z-control data to a host computer 21 as the irregularity data of a sample. At a mirror body 31 at the lower end of the XYZ-driving piezoelectric body 28, an X-displacement detecting sensor 33 and a Y-displacement sensor 34 are provided. The X control part 24 comprises an A-scanning D/A converter 24a, an X-offset D/A converter 24b, an X-displacement A/D converter 24c and an adder 24d. The Y control part 25 comprises a Y-scanning D/A converter 25a, a Y-offset D/A converter 25b, a Y-displacement A/D converter 25c and an adder 25d.