The exposure device is able to supply only EUV radiation to a mask, while eliminating radiation other than the EUV radiation. A multi layer made from a plurality of Mo/Si pair layers is provided upon the front surface of a mirror, and blazed grooves are formed in this multi layer. Radiation which is incident from a light source device is incident upon this mirror, and is reflected or diffracted. Since the reflected EUV radiation (including diffracted EUV radiation) and the radiation of other wavelengths are reflected or diffracted at different angles, accordingly their directions of progression are different. By eliminating the radiation of other wavelengths with an aperture and/or a dumper, it is possible to irradiate a mask only with EUV radiation of high purity.