A phase contrast microscope includes: an illumination light emission unit that emits illumination light for phase difference measurement to a container in which a liquid and an observation target are contained; an imaging unit that images the observation target irradiated with the illumination light; an adjustment optical system that adjusts refraction of the illumination light due to a liquid surface shape of the liquid in the container; a liquid surface shape estimation unit that estimates the liquid surface shape of the liquid in the container based on a brightness distribution of a phase difference image of the observation target captured by the imaging unit; and an adjustment information acquisition unit that acquires adjustment information for adjusting optical characteristics of the adjustment optical system based on the liquid surface shape estimated by the liquid surface shape estimation unit.