There are provided a reflective photomask blank and a reflective photomask, which are compatibly capable of suppressing a shadowing effect and improving the life of a mask. A reflective photomask blank (10) includes a substrate (1), a reflection part (7) provided on the substrate (1) and configured to reflect incident light, and a low reflection part (8) provided on the reflection part (7) and configured to absorb incident light. The low reflection part (8) has a multi layer structure of at least two layers or more layers. An outermost layer (5) of the low reflection part (8) has a refractive index n equal to or more than 0.90 and an extinction coefficient k equal to or less than 0.02 with respect to extreme ultraviolet (EUV) light (where a wavelength is 13.5 nm).