A mask blank for EUV lithography (EUVL) excellent in in-plane uniformity of the peak reflectivity of light in the EUV wavelength region and in in-plane uniformity of the center wavelength of reflected light in the EUV wavelength region, at the surface of a multilayer reflective film, and a process for its production, as well as a substrate with reflective layer for EUVL to be used for the production of such a mask blank for EUVL, and a process for its production. A substrate with reflective layer for EUVL having a reflective layer for reflecting EUV light formed on a substrate, where the reflective layer is a multilayer reflective film having a low refractive index layer and a high refractive index layer alternately stacked plural times.