PURPOSE: To enable a sample image to be observed under the optium condition irrespective of the variation of an acceleration voltage by providing a means of controlling the position of the optical axis direction of a sample, which is inserted inside the magnetic field of an objective lens, according to the acceleration voltage value of an electron gun.

CONSTITUTION: A sample device 19a, which is constituted by incorporating both a slanting mechanism and a vertically moving mechanism into a sample holder, is inserted into the upper part of an objective lens 14, which is located on the optical axis (Z), so that the device 19a can be controlled with a driving equipment 19b. A signal sent from an acceleration-voltage controlling circuit 20, which controls the acceleration voltage of electron rays used in an electron gun 11, is applied to a vertical-sample-movement controlling means 21 so as to adjust the position of the optical axis of a sample to a specific position according to the value of the acceleration voltage. As a result, the aberration of the lens 14 can be suppressed low even when the electron microscope is not used at the maximum acceleration voltage. Besides, sample observation can be carried out under the optimum condition irrespective of the variation of the acceleration voltage.