a microscope includes a revolver on which are mounted at least three objective lenses having different magnifications , a driving device for revolving the revolver to switch the objective lens disposed in an optical path of the microscope , an operating device capable of giving a plurality of drive commands for disposing a desired objective lens in the optical path of the microscope to the driving device and an invalidating element for invalidating a specified drive command among the drive commands . the specified drive command serves to switch the objective lens disposed in the optical path of the microscope from a first objective lens having a minimum magnification to a second objective lens having a maximum magnification among the objective lenses .