For a semiconductor device S as an inspected object, there are provided an image acquisition part 1, an optical system 2 including an objective lens 20, and a solid immersion lens (SIL) 3 movable between an insertion position including an optical axis from the semiconductor device S to the objective lens 20 and a standby position off the optical axis. Then observation is carried out in two control modes consisting of a first mode in which the SIL 3 is located at the standby position and in which focusing and aberration correction are carried out based on a refractive index n0 and a thickness t0 of a substrate of the semiconductor device S, and a second mode in which the SIL 3 is located at the insertion position and in which focusing and aberration correction are carried out based on the refractive index n0 and thickness t0 of the substrate, and a refractive index n1, a thickness d1, and a radius of curvature R1 of SIL 3. This provides a microscope and a sample observation method capable of readily performing observation of the sample necessary for an analysis of microstructure or the like of the semiconductor device.