An optical measurement method includes: preparing an optical
system for recording a hologram caused by modulating, with a
reference beam, an object beam obtained by illumination of a sample with illumination light, the
reference beam being coherent to the illumination light; arranging a calibration unit on an
optical path of the illumination light in a state where there is no sample, the calibration unit including an optical
system that produces a known optical wave distribution; recording a first hologram caused while the calibration unit is producing an optical wave distribution; and calculating information about an optical wave distribution of the
reference beam based on information indicating a position where the calibration unit is arranged, the known optical wave distribution, and the first hologram.