A mounting device for a mirror comprises a hollow body (2) and a cover (3) configured to be connected to each other tightly so as to define an internal cavity between them, wherein the hollow body (2) delimits a hole (19) configured to be connected tightly with a vacuum source, and the cover (3) delimits a through opening (10) for the entry of an electromagnetic radiation into the internal cavity, a mirror (23) connected to the hollow body (2) by means of a mobile support (22), adjustment members configured to adjust the position and inclination of the support (22) with respect to the hollow body (2), magnetic rotators (51) connected externally to the cover (3), through a sealed connection, and configured to be operationally connected to the adjustment members.