A catadioptric projection optical system for projecting an image of an object onto an image plane through two intermediate image formations. The catadioptric projection optical system includes a first optical system, for receiving light from the object, including a plurality of lenses, a second optical system, for forming the image of the object on the image plane, including a plurality of lenses, and a third optical system disposed optically between the first optical system and the second optical system. The third optical system includes a first concave mirror and a second concave mirror. The light is reflected by the first concave mirror then by the second concave mirror to be directed to the second optical system along a z-shaped optical path, and the first, second and third optical systems have a common straight optical axis.