A stereomicroscope includes a first beam path and a second beam path, wherein in the first beam path a first telescope system is provided and in the second beam path a second telescope system is provided. An observation unit comprising a first and a second observation unit is also provided. At least one optical element of the first telescope system compared to at least one corresponding optical element of the second telescope system has a different optically effective diameter. Between the first telescope system and the second telescope system and the first and the second observation units a prism group is provided which can be moved in the beam path of the first telescope system with the larger diameter of the entrance pupil.