Provided is a scanning near-field optical microscope capable of obtaining, in a highly sensitive manner, optical information having a spatial frequency higher than a spatial frequency corresponding to a wavelength of irradiation light. A scanning near-field optical microscope 100 according to the present invention includes: a light irradiating part 102 for emitting illumination light toward a sample 107; a light receiving part 112 for receiving light; a microstructure for generating or selectively transmitting near-field light, the microstructure being disposed on at least one of an emission side of the light irradiating part 102 and an incident side of the light receiving part 112; and an ultrahigh-wavenumber transmitting medium 108 for transmitting near-field light, the ultrahigh-wavenumber transmitting medium exhibiting anisotropy in permittivity or permeability.