A specimen and an objective lens can be quickly brought close together or separated without an operator being concerned about the positional relationship between the specimen and the objective lens, and once the correct positional relationship is established, the focal position can be finely adjusted. The invention includes a first focusing mechanism for moving the objective lens in an optical axis direction relative to the specimen so as to approach the specimen or withdraw therefrom; a second focusing mechanism for displacing an internal optical system in the optical axis direction, and a switching device for switching between operating the first focusing mechanism and operating the second focusing mechanism when the objective lens is disposed at a predetermined switching position.