Using a solid immersion lens (SIL) having a spherical lens surface with a radius of curvature R_L from a material having a refractive index n_L, an image of a sample is observed. A geometric aberration characteristic caused by the SIL is evaluated by using a predetermined optical system. Using a coefficient k (0k1) set to satisfy a condition where the average image surface becomes flat or a condition yielding a favorabl chromatic aberration characteristic, the sample is observed with the solid immersion lens while a surface, orthogonal to the optical axis, including a point located downstream of the spherical center c of the lens surface 10 by (k(R_L/n_L) along the optical axis, is employed as a sample observation surface 20. This realizes a sample observation method that can observe the image of the sample favorably with a solid immersion lens, and the solid immersion lens.