AUTO-FOCUS METHOD IN SCANNED TYPE CHARGED PARTICLE BEAM DEVICE AND SCANNED TYPE CHARGED PARTICLE BEAM DEVICE

PROBLEM TO BE SOLVED: To realize an auto-focus method in the scanned type charged particle beam device in which a precise focused position is obtained in any sample surface shape or observation magnification, and a scanned type charged particle beam device. SOLUTION: Electron beams 1 are focused on a sample 5 and the beams are scanned two-dimensionally in the prescribed region on a sample. At this, the focusing state of the beams on the sample is changed step by step, and a specific region on the sample is scanned by the beams in the stage of each focus. The detected signals obtained by the beam scanning are passed through a plurality of high pass filters of plural different frequency passage bands, and the signals at each frequency band are integrated. And the integration values at each focusing step are stored, and based on this sequence of numbers of the integration value, the peak accuracy is judged. And by comparing the plural peak accuracy judged, any of the peak position is selected, and the focusing state of the beams is set on the focusing state of the electron beam that corresponds to the peak position as selected.