1. An inverted microscope that allows observation of a specimen from underneath, the inverted microscope comprising: an objective lens holding unit that holds an objective lens configured to collect at least observation light from the specimen; a tube lens configured to focus the observation light collected by the objective lens; a branching unit configured to branch an optical path of the observation light from the tube lens; an observation image switching device which is removably provided in a microscope main body between the objective lens and the tube lens and which is configured to switch between wavelengths of an observation image or between magnifications of the observation image, wherein the observation image switching device includes a filter switching unit which has a plurality of absorption filters for absorbing light of wavelengths other than a specified wavelength and which is configured to cause one of the plurality of absorption filters to be arranged on an optical axis of the objective lens; a light source unit which includes a plurality of excitation filters for transmitting light of a specific wavelength to excite a fluorophore in the specimen and which is configured to select a wavelength of light to be introduced into the microscope main body by switching between the excitation filters; a dichroic mirror configured to selectively reflect or transmit the light of the specific wavelength from the light source unit; and a control unit configured to synchronize a switching operation between the absorption filters with a switching operation between the excitation filters.