Axial adjustments of an aberration corrector are made roughly. Whenever plural values of voltage are applied to an electrode in the first stage of the corrector, a different value of voltage is applied to the electrodes in the stage whose center is passed through by the reference orbit in the aberration corrector. At this time, a scanning deflector scans the electron beam over a specimen, producing a scanned image signal. Based on the scanned image signal, the amounts of positional deviations of the image are calculated. Based on the calculated amounts of positional deviations and on the voltages applied to the electrode in the first stage, an optimum value of voltage is calculated and fed back to the electrode in the first stage of the corrector.