The invention relates to an optical system that has reduced power consumptions, ensures noiseless operations and fast responses, contributes to cost reductions due to simplified mechanical structure, and, albeit having a small outside diameter and small size, is capable of focusing and zooming. The optical system of the invention comprises a variable mirror and a moving optical element group. The optical element group has a zooming function, and the variable mirror has a focusing function. An optical apparatus of the invention comprises such an optical system as mentioned above.