A substrate stage is used in a lithographic apparatus. The substrate stage includes a substrate table constructed to hold a substrate and a positioning device for in use positioning the substrate table relative to a projection system of the lithographic apparatus. The positioning device includes a first positioning member mounted to the substrate table and a second positioning member co-operating with the first positioning member to position the substrate table. The second positioning member is mounted to a support structure. The substrate stage further comprises an actuator that is arranged to exert a vertical force on a bottom surface of the substrate table at a substantially fixed horizontal position relative to the support structure.