In an SEM observation in a depth direction of a cross section processed by repeated FIB cross-sectioning and SEM observation to correct a deviation in an observation field of view and a deviation in focus, are corrected, the deviations occurring when a processed cross section moves in the depth direction thereof; information on a height and a tilt of a surface of cross section processing area is calculated before the processing, the above information is used, the deviation in a field of view and the deviation in focus in SEM observation, which correspond to an amount of movement of the cross section at a time of the processing, are predicted, and the SEM is controlled based on the predicted values.