A laser scanning microscope and method for adjusting a laser scanning microscope. The microscope has an optical system which has a light guiding fiber between the first light source and the third beam deflection unit and has no light guiding fibers between the second light source and the third beam deflection unit. In this way, the second light source can be used as an adjustment reference for the first and second beam deflection units. The adjustment can be implemented using test images recorded by means of the third and fourth beam deflection units; additional sensors or internal calibration samples are not required.