A reflective mask blank includes: a substrate; a multilayer reflective film configured to reflect EUV light; a protective film; and a phase shift film configured to shift a phase of EUV light, in this order, in which the phase shift film includes a first layer including one or more first elements selected from a group consisting of ruthenium, rhenium, iridium, silver, osmium, gold, palladium, and platinum, and a second layer including one or more second elements selected from a group consisting of tantalum and chromium, the first layer includes a region A1 in which a content of an element having a highest content among the one or more first elements increases in a thickness direction from a side opposite to the second layer toward the second layer, and the region A1 is present adjacent to the second layer.