Abstract: A microscope has an optical system in which the number of photographing optical paths can be increased. The optical system includes a light source, an illuminating optical system for radiating the illuminating light to a sample, an objective lens which is opposed to the sample, an imaging lens, which is arranged in an optical path of light passed through the objective lens, a first beam splitting block, arranged in an optical path between the objective lens and the primary image, for splitting the light passed through the imaging lens into at least three different directions, a second beam splitting block for splitting one of the light split by the first beam splitting block into a plurality of directions, an observation optical path which receives the light split by the second beam splitting block, and a plurality of photographing optical paths provided for the split light, wherein images of the same magnification are formed.