A photomask blank which is to be processed into a photomask suitable for pattern transfer using exposure light of wavelength 250 nm or below, comprising a transparent substrate and a chromium-containing film disposed on the substrate, directly or through an optical film, wherein said chromium-containing film is constituted by a single chromium compound layer or by two or more chromium compound layers (21,22,23), the or each chromium compound layer being formed of a chromium compound containing chromium and nitrogen, or chromium, nitrogen and oxygen, and having a composition with a chromium content of at least 30 at% and a total content of chromium, nitrogen and oxygen of at least 93 at%, and meeting formula: 3 ⁢ Cr ≤ 2 ⁢ O + 3 ⁢ N wherein Cr is chromium content (at%), 0 is oxygen content (at%) and N is nitrogen content (at%), the chromium-containing film has a sheet resistance of not more than 10 000 Ω/□, and wherein (i) when said chromium-containing film is said single chromium compound layer, the chromium compound layer has a first composition, namely a composition wherein the atomic ratio of nitrogen/chromium is at least 0.95, chromium content is at least 40 at%, the total content of chromium and nitrogen is at least 80 at%, and oxygen content is not more than 10 at%, (ii) when said chromium-containing film is constituted by two or more said chromium compound layers, the chromium compound layers include at least one chromium compound layer having a said first composition with the atomic ratio of nitrogen/chromium of at least 0.95, chromium content of at least 40 at%, total content of chromium and nitrogen of at least 80 at%, and oxygen content of up to 10 at%, and the total thickness of said one or more chromium compound layers having a said first composition is more than 70% and up to 100% of the overall thickness of the chromium-containing film; and wherein: where the chromium-containing film is disposed on the transparent substrate directly, said chromium-containing film has an optical density of 2.5 to 3.5 with respect to the exposure light; and where the chromium-containing film is disposed on the transparent substrate through a said optical film, and the optical film comprises a phase shift film formed of a material containing silicon and free of transition metal, or of a material containing silicon and transition metal, the sum of the optical densities of the chromium-containing film and the phase shift film with respect to the exposure light is from 2.5 to 3.5. (i) when said chromium-containing film is said single chromium compound layer, the chromium compound layer has a first composition, namely a composition wherein the atomic ratio of nitrogen/chromium is at least 0.95, chromium content is at least 40 at%, the total content of chromium and nitrogen is at least 80 at%, and oxygen content is not more than 10 at%, (ii) when said chromium-containing film is constituted by two or more said chromium compound layers, the chromium compound layers include at least one chromium compound layer having a said first composition with the atomic ratio of nitrogen/chromium of at least 0.95, chromium content of at least 40 at%, total content of chromium and nitrogen of at least 80 at%, and oxygen content of up to 10 at%, and the total thickness of said one or more chromium compound layers having a said first composition is more than 70% and up to 100% of the overall thickness of the chromium-containing film; and wherein: where the chromium-containing film is disposed on the transparent substrate directly, said chromium-containing film has an optical density of 2.5 to 3.5 with respect to the exposure light; and where the chromium-containing film is disposed on the transparent substrate through a said optical film, and the optical film comprises a phase shift film formed of a material containing silicon and free of transition metal, or of a material containing silicon and transition metal, the sum of the optical densities of the chromium-containing film and the phase shift film with respect to the exposure light is from 2.5 to 3.5. where the chromium-containing film is disposed on the transparent substrate directly, said chromium-containing film has an optical density of 2.5 to 3.5 with respect to the exposure light; and where the chromium-containing film is disposed on the transparent substrate through a said optical film, and the optical film comprises a phase shift film formed of a material containing silicon and free of transition metal, or of a material containing silicon and transition metal, the sum of the optical densities of the chromium-containing film and the phase shift film with respect to the exposure light is from 2.5 to 3.5.