Provided is a mask blank which enables EB defect correction to be suitably applied and which further enables a reduction in the thickness of a light-shielding film. A mask blank 10 is used for producing a transfer mask adapted to be applied with ArF exposure light and has a light-shielding film 2 on a transparent substrate 1. The light-shielding film 2 has an at least two-layer structure comprising a lower layer composed mainly of a material containing a transition metal, silicon, and at least one or more elements selected from oxygen and nitrogen and an upper layer composed mainly of a material containing a transition metal, silicon, and at least one or more elements selected from oxygen and nitrogen. The ratio of the etching rate of the lower layer to that of the upper layer is 1.0 or more and 20.0 or less in etching which is carried out by supplying a fluorine-containing substance to a target portion and irradiating charged particles to the target portion.