PURPOSE: To simplify the structure, reduce the thickness, easily make optical adjustments, and make an observation at an easy attitude by holding an image forming lens and a deflecting mirror integrally on a holding member and constituting them movably to a housing.

CONSTITUTION: A mount 2 for fitting to a microscope main body is provided at the lower part of the housing 1, and a binocular mount 3 for fitting binocular lens barrels and a photographic device fitting mount 4 for fitting a photographic device are provided at the upper part. The part between the microscope main body and binocular lens barrels is made afocal. The holding member 21 is inserted movably into the lens barrel part 1c of the optical path 8 of the housing 1. Then a sample image 11 is formed off the center axis of the cylinder of the photographic device fitting mount 4, and the holding member 21 is shifted in the plane perpendicular to the optical axis 8a so as to match the image formation position with the center axis. Then an image forming lens 9 and a deflecting mirror 10 move together with the holding member 21 and the sample image 11 comes to the center axis of the cylinder of the photographic device fitting mount 4.