PURPOSE: To coincide a desired region with the center of a viewing field without marking on a slide glass by deciding the relative position of a previous and a present slide glasses and enabling the coordinate transformation to be performed.

CONSTITUTION: A slide glass S is a rectangle ABCD, datum points are three points of a point E, a point F and a point G. A point Hi represents an object to be examined such as a cell. A rectangle A'B'C'D' is a slide glass S mounted at the time of laser examination with microscope. At the time of the previous examination with microscope, the coordinates of two points G, F on an arbitrarily selected side of the slide glass S and a point E on another side adjacent to the former side are read out, at the time of present examination with microscope, the coordinates of arbitrarily selected three points of two points G', F' on a side and a point E' on another side are also read out, the relative position of the previous and the present slide glasses S is determined and the coordinate transformation is enabled to be performed. Consequently, the coordinate Hi of the object to be examined read and stored at the time of previous examination by microscope is transformed according to the transformed coordinate value of the slide glass S, the slide glass is moved and the coordinate Hi appears automatically at the center of the viewing field.