To improve versatility of illumination of a microscope.

A light projection tube unit 101 is releasably attached to a microscope body and allows a vertical illumination module 103, a total reflection illumination module 104, and a spot illumination module 105 to be attached to and detached from an incident section 101A. When illumination light from the illumination module attached to the incident section 101A enters, spreading luminous flux thereof, the illumination light which passes through lenses 271 through 274 and exits from a projection section 101C forms an image on the image-side focal plane of the objective lens of the microscope. When the illumination light from the illumination module enters as parallel luminous flux, the illumination light which passes through the lenses 271 through 274 and exits from the projection section 101C enters the image-side focal plane of the objective lens of the microscope as parallel luminous flux.