To provide a microscope for observing a sample by either of projected light and transmitted light by arranging the sample between tow objective lenses.

In the case of a field switching type microscope, two objective lenses 2 and 3 of nearly the same optical characteristic data are provided and a mirror 5 is installed in the rear of at least one of these lenses 2 and 3. Then, light transmitted through a sample is returned accurately to an original position by reflection to realize double light transmission to a preparation under the best spatial illumination effect. In the case of a laser scanning microscope, two objective lenses having the same optical characteristic data are similarly provided and a phase conjugate mirror or a compensation mirror is installed in the rear of at least one of the lenses.