A light sheet microscope includes an objective, an illumination optical system, a correction device, an image pickup device, a first adjustor, a second adjustor and a controller. The controller performs a first focus process and a spherical aberration correction process. The first focus process is a process in which the first adjustor is controlled on the basis of light that is from the light sheet plane and that is detected via the objective so that the light sheet plane and a focal plane become closer when a relative position between the light sheet plane and a sample has been changed. The spherical aberration correction process is a process in which the correction device is controlled so that an evaluation value of the image obtained by the image pickup device becomes greater when the first adjustor has changed the relative position between the light sheet plane and the objective.