A light blocking member (18) for application, to a microscope is provided. Although it is producible at a sufficiently low cost, it can sufficiently block ambient light, and does not require a special operation when a sample (16) is placed on a stage (2) or the sample is taken out from above the stage.The light blocking member (18) is formed from a soft polymer, has an inner peripheral surface which is cylindrical in at least an upper part thereof, and is held on an objective lens assembly by fitting the upper part onto the outer peripheral surface of the objective lens assembly.