An inorganic material film containing tin within the concentration range of 0.1 atomic percent or higher but no higher than 11.5 atomic percent eliminates the problem in which tin localizes and forms into particles, with the result that these particles turn into defects in an optical film. An inorganic material film for a photomask blank according to the present invention film-formed by sputtering and composed of a chromium-containing material includes a light-shielding layer having electrical conductivity, wherein the light-shielding layer contains 0.1 atomic percent or higher but no higher than 11.5 atomic percent of tin and no higher than 15 atomic percent of oxygen. The lower limit of oxygen concentration is, for example, 3 atomic percent. The inorganic material film has electrical conductivity, which is preferably no higher than 5000 Ω/cm² when evaluated in terms of resistance values.

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