A lens tube of a microscope includes a plurality of observation ports, and first and second optical path switching portions that move relative to each other for switching an optical path to an arbitrary one of the observation ports. The first optical path switching portion can switch for guiding light from a specimen to the second optical path switching portion through a first optical element of the first optical path switching portion, or for guiding the light to the second optical path switching portion iwthout passing through the first optical element. The second optical path switching portion can switch for guiding the light from the first optical path switching portion to an arbitrary one of the observation ports through a second optical element of the second optical path switching portion, or for guiding the light to an arbitrary one of the observation ports without passing through the second optical element.