A high-sensitivity reflection measurement apparatus disposed in an optical path between a light emitter and a detector of an analysis apparatus comprises an incident-side optical element, which bends the optical path of measurement light emitted from the light emitter such that the angle of incidence of the measurement light so emitted with respect to a sample surface under measurement ranges from 70.degree. inclusive to 90.degree. exclusive with respect to the direction perpendicular to the sample surface under measurement. The measurement light is transmitted as linearly polarized light having a desired oscillation direction, and is incident on the sample surface under measurement. Information related to the measured sample surface is obtained from light reflected from the measured sample surface when the linearly polarized light from the incident-side optical element is incident on the sample surface.