There is disclosed a photo mask blank comprising at least a light-shielding film containing Cr and one or more layers of an anti-reflection film disposed on a substrate, wherein at least one layer of the anti-reflection film contains any one selected from the group consisting of silicon oxide, silicon nitride and silicon oxynitride. And there is also disclosed a photo mask blank comprising at least a light-shielding film containing Cr and two or more layers of an anti-reflection film disposed on a substrate, wherein the anti-reflection film comprises at least a layer of film with high transmittance at exposure wavelength, and a layer of film with lower transmittance at exposure wavelength than that of the layer and higher transmittance at inspection wavelength than at that exposure wavelength. Thus, there can be provided a photo mask blank having an anti-reflection film that can sufficiently reduce reflectance even if the exposure wavelength is short.