A mask blank suitable for fabricating a phase shift mask having a thin film pattern composed of a material enabling dry etching with a fluorine-based gas and a substrate-engraved pattern. The mask blank 100 is used to fabricate a phase shift mask having a thin film pattern and a substrate-engraved pattern. The mask blank 100 has a structure in which an etching stopper film 2, a thin film for pattern formation 3 and an etching mask film 4 are laminated in this order on a transparent substrate 1. The etching stopper film 2 is made of a material that contains chromium and oxygen and the oxygen content thereof is more than 50 at %. The thin film 3 is made of a material that can be dry-etched by a fluorine-based gas. The etching mask film 4 is made of a material that contains chromium, the chromium content thereof is not less than 45 at %, and the oxygen content thereof is not more than 30 at %.