An inverted microscope includes: a microscope main body; a stage that is supported by the microscope main body; and an observation optical system that allows observing a sample placed on the stage from underneath, the microscope main body, in which an optical device can be attached between an objective lens and a tube lens which constitute the observation optical system including a plurality of stage supporting parts that support the stage; and a beam part that connects, in a manner of locating between the tube lens and the objective lens, at least a pair of stage supporting parts at front and back sides together among the plurality of stage supporting parts.