A cross-section processing-and-observation method, including a cross-section exposure step in which a sample is irradiated with a focused ion beam to expose a cross-section of the sample, and a cross-sectional image acquisition step in which the cross-section is irradiated with an electron beam to acquire a cross-sectional image of the cross-section. The cross-section exposure step and the cross-sectional image acquisition step are repeatedly performed along a predetermined direction of the sample at a setting interval to acquire multiple cross-sectional images of the sample. The method also includes a specific observation target detection step in which a predetermined specific observation target from the cross-sectional image acquired a the cross-sectional image acquisition step is detected. In the specific observation target detection step, after a predetermined specific observation target is detected, the setting interval of the cross-section exposure step is set to be shorter than that before the specific observation target is detected.