An exposure apparatus that exposes an image of a pattern of a mask onto a photosensitive substrate with EUV radiation, and includes a radiation source unit and an exposure apparatus body unit. The exposure apparatus body unit includes an optical integrator, a mirror arranged in an optical path between the radiation source unit and the optical integrator, a detector arranged in an optical path of the exposure apparatus body unit, and a controller which is connected to the detector and which controls an inclination of the mirror based on an output from the detector. In addition, the radiation source unit and the exposure apparatus body unit are installed independently.