To insert the edge part of an objective in a laboratory animal being an observation object with only a low damage, and to set the edge part of the objective in an electrically insulated state.

The microscope objective 1 is equipped with a metallic lens frame 17 holding a front lens 21, and the electric insulating member 6 disposing the lens frame 17 in the electrically insulated state from a microscope main body. The electric insulating member arranged on an optical axis between the microscope objective 1 and the microscope main body 2 and having the same screw diameter on both sides is used.