A cross-section processing and observation method including: acquiring a surface image by scanning and irradiating a surface of a sample with ion beam; setting, on the surface image, a first sliced region and a second sliced region for performing the slice processing, the second sliced region being adjacent to the first sliced region and having a longitudinal length obtained by subtracting a slice width of the second sliced region from a longitudinal length of the first sliced region; forming a cross-section by irradiating the first sliced region and the second sliced region with the ion beam; and acquiring a cross-sectional image by irradiating the cross-section with electron beam.