The present invention provides a lithographic apparatus comprising an illumination system for providing a projection beam of radiation. The illumination system comprises at least one movable optical element (7), such that a projection beam of radiation (4) can be shifted around a central position. This ensures that inhomogeneities in the intensity distribution in the projection beam (4) will be smeared out, which in turn provides an improved homogeneity of the exposure of a surface to be illuminated by the system, such as a wafer or other substrate. The optical element (7) may comprise a motor movable mirror, prism, filter, lens, axicon, diffuser, diffractive optical array, optical integrator, etc. The invention further provides a device manufacturing method, using a lithographic apparatus according to the invention, wherein the optical element is moved, in order to provide an optimum homogeneity for the projection beam of radiation.