A beam regulating apparatus for an EUV illumination beam has a position sensor device and a control/regulating device, which is signal-connected to the position sensor device. Furthermore, at least one beam regulating component which influences the beam path of the illumination beam is signal-connected to the control/regulating device. The position sensor device has at least one diffraction grating for generating at least two reference partial beams from the illumination beam. Furthermore, the position sensor device has a respective position sensor assigned to one of the reference partial beams, for detecting the assigned reference partial beam. This results in a beam regulating apparatus which enables well-controllable illumination in conjunction with a simple construction.