A projection optical system is configured to project an image of an object plane onto an image plane, and includes a first optical element having an aspheric shape that is rotationally asymmetric with respect to an optical axis, a moving unit configured to move the first optical element in a direction perpendicular to the optical axis, and a second optical element fixed on the optical axis, and configured to reduce an optical path length difference caused by an aspheric surface of the first optical element, the second optical element having no aspheric shape complement to the aspheric shape of the first optical element.