To provide a device and method for cleaning mirror by which a mirror having deposits, such as the debris etc., generated from an EUV light source and lowered in reflectance can be made reusable by removing the debris etc., in a vacuum; and to provide EUV optical illumination equipment and an exposure device containing the mechanism of the device and method.

The mirror which reflects EUV light with its light source of a wave length of ≤60 nm can be made reusable by cleaning the mirror in a vacuum, by removing the deposits adhering to the surface of the mirror by projecting an ion beam upon the mirror in a vacuum chamber which can be exhausted to a vacuum. The EUV light can be supplied continuously from the optical illumination equipment without any time loss by washing the mirror, after the mirror is transported in a vacuum by connecting the device having such mechanism to the optical illumination equipment and exposing device.