When injection of electrons into a sample supporting member causes a potential gradient between an insulative thin film and a conductive thin film at a site of electron beam injection, the potential barrier of the surface of the insulative thin film becomes thin, and an electron emission phenomenon is caused by tunnel effects. Secondary electrons caused in the insulative thin film tunnel to the conductive thin film along the potential gradient. The secondary electrons, having tunneled, reach a sample while diffusing in the conductive thin film. In the case where the sample is a sample with a high electron transmittance, such as a biological sample, the secondary electrons also tunnel through the interior of the sample. The secondary electrons are detected to acquire an SEM image in which the inner structure of the sample is reflected.