To provide an optical element switching device in which a vibration and an impact is reliably alleviated during the positioning of a mechanical positioning mechanism, and to provide an optical microscope provided with the same and an optical element switching method.

The optical element switching device 10 which switches a plurality of optical elements 25 to arrange them on the optical path 20a of an optical device, is provided with a mounting member 14 on which the optical elements 25 are mounted and which can move along a direction orthogonal to the optical path 20a, and a positioning member 13 which mechanically positions the mounting member 14 at a point where any one of the optical elements 25 mounted on the mounting member 14 is arranged on the optical path 20a. A mechanical contact portion between the mounting member 14 and the positioning member 13 is coated with grease having a number of worked penetration (JIS K 2220) 4 or 5.