To optionally select the insertion/detachment of a dimming member to/from an illumination optical path at switching from a dark filed illumination to a bright field illumination in accordance with the kinds of sample and the purpose of microscopic inspection.

As for the bright/dark field vertical illuminating device for the microscope for vertically illuminating the dark field and the bright field by switching a reflection mirror and an illuminating lens, the device is provided with optical path switching frames 7 and 17 which are provided with dark field illuminating optical systems 9, 10, 11, 12 and 18 and a bright field illuminating optical system and which is movably loaded on the main body frame 1, the dimming member 19 which is loaded on the main body frame 1 so that it may be moved in parallel to the moving direction of the optical path switching frames 7 and 17 at switching to the bright field illumination, and connecting mechanisms 14, 15 and 16 capable of selecting so that the optical path switching frames 7 and 17 and the dimming member 19 may be integrally or individually moved to the illumination optical path (n).