The present invention aims to provide a reflective mask blank and a reflective mask which have a highly smooth multilayer reflective film as well as a low number of defects, and methods of manufacturing the same, and aims to prevent charge-up during a mask defect inspection using electron beams.The present invention provides a reflective mask blank for EUV lithography in which a conductive underlying film, a multilayer reflective film that reflects exposure light, and an absorber film that absorbs exposure light are layered on a substrate, wherein the conductive underlying film is a single-layer film made of a tantalum-based material or a ruthenium-based material with a film thickness of greater than or equal to 1 nm and less than or equal to 10 nm that is formed adjacent to the multilayer reflective film, or the conductive underlying film is a multilayer film including a layer of a tantalum-based material with a film thickness of greater than or equal to 1 nm and less than or equal to 10 nm that is formed adjacent to the multilayer reflective film and a layer of a conductive material that is formed between the layer of the tantalum-based material and the substrate. The present invention also provides a reflective mask manufactured using the reflective mask blank. Furthermore, a semiconductor device is manufactured using the reflective mask.