A microscope for introducing light from a light source via an objective lens to a sample so that a user observes the sample via the objective lens includes: a minute opening arranged in an optical path between the light source and the objective lens and on a focal plane of the image side of the objective lens or at a position conjugate with its conjugate plane; position adjusting means for adjusting the position of the minute opening so that the light from the light source via the minute opening is incident to the sample at the Brewster's angle; an polarizing element arranged in the optical path between the light source and the objective lens for extracting rectilinear polarized light from the light from the light source and applying the rectilinear polarized light to the sample.