The present invention relates to the acquisition of tilted series images of a minute sample in a short time.The present invention relates to: measuring in advance the relation between an amount of focus shift and a degree of coincidence at the time of acquiring tilted series images; calculating backwards a focus shift from the degree of coincidence on the basis of this relation; correcting the focus shift by controlling a stage, an objective lens, and the like; and thus acquiring the tilted series images. In addition, the present invention relates to: acquiring a reference image in advance at the time of photographing the tilted series images; obtaining the correlation between an acquired image and the reference image; and performing, if the degree of coincidence is equal to or smaller than a set value, processing such as the transmission of a warning message and the stop of an image acquisition sequence. According to the present invention, it becomes possible to perform focusing at the time of photographing the tilted series images at high speed, so that the length of time for photographing the tilted series images can be shortened. In addition, an image inappropriate for three-dimensional reconstruction can be removed. This makes it possible to enhance the throughput of failure analysis of a semiconductor and an advanced material.