Conventionally, in a general-purpose scanning electron microscope, the maximum accelerating voltage which can be set is low, and hence thin crystal samples which can be observed under normal high-resolution observation conditions are limited to samples with large lattice spacing. For this reason, there has no means for accurately performing magnification calibration. As means for solving this problem, the present invention includes an electron source which generates an electron beam, a deflector which deflects the electron beam so as to scan a sample with the electron beam, an objective lens which focuses the electron beam on the sample, a detector which detects an elastically scattered electron and an inelastically scattered electron which are transmitted through the sample, and an aperture disposed between the sample and the detector to control detection angles of the elastically scattered electron and the inelastically scattered electron. The electron beam enters the sample at a predetermined convergence semi-angle, and a lattice image is acquired at a second convergence semi-angle larger than a first convergence semi-angle at which a beam diameter is minimized on the sample.