1. A cross-section processing-and-observation method comprising: a cross-section exposure step of irradiating a sample with a focused ion beam to expose a cross-section of the sample; a cross-sectional image acquisition step of irradiating the cross-section with an electron beam to acquire a cross-sectional image of the cross-section; and a step of repeatedly performing the cross-section exposure step and the cross-sectional image acquisition step along a predetermined direction of the sample at a setting interval to acquire a plurality of cross-sectional images of the sample, wherein in the cross-sectional image acquisition step, a cross-sectional image is acquired under different condition settings for a plurality of regions of the cross-section.