A light sheet microscope includes an objective, an illumination optical system, a first adjustor, a second adjustor and a controller. The illumination optical system irradiates sample with a light sheet from a direction that is different from an optical axis direction of the objective. The first adjustor adjusts a relative position between a light sheet plane on which the light sheet is formed and the objective in an optical axis direction of the objective. The second adjustor adjusts a relative position between the light sheet plane and the sample in an optical axis direction of the objective. The controller controls the first adjustor on the basis of light that is from the light sheet plane and that is detected via the objective when a relative position between the light sheet plane and the sample is changed by the second adjustor.