To provide an extreme ultraviolet optical barrel or the like which is capable of reducing the adverse effect of a flare (scattering of extreme ultraviolet).

The reflection optical lens barrel is equipped with six aspherical mirrors M1 to M6, holding mechanisms K1 to K6 holding the mirrors M1 to M6 and a position adjusting mechanism, and shading plates P1 to P6 and the like arranged adjacent to the mirrors M1 to M6. The shading plates P1 to P6 are made of material of high heat emissivity (0.7 or above)/high heat conductivity, so that they are restrained from rising locally in temperature by diffusing heat in a short time. The sizes of apertures P1a to P6a provided to the shading plates P1 and P6 are so set as not to block regular reflected light fluxes (effective light flux, or light flux described by so-called ray trace) reaching the effective reflecting surfaces of the corresponding mirrors M1 to M6, and the apertures P1a to P6a are so formed as to get minimal in area.