A reflective mask blank includes, on/above a substrate in the following order from the substrate side a multilayer reflective film which reflects EUV light and an absorber film which absorbs EUV light. The absorber film is a tantalum-based material film containing a tantalum-based material. The absorber film provides a peak derived from the tantalum-based material in an X-ray diffraction pattern, the peak having a peak diffraction angle (2θ) of 36.8 degrees or more and a full width at half maximum of 1.5 degrees or more.