A mask blank is used for manufacturing a binary mask adapted to be applied with ArF excimer laser exposure light and has a light-shielding film for forming a transfer pattern on a transparent substrate. The light-shielding film has a laminated structure of a lower layer and an upper layer and has an optical density of 2.8 or more for the exposure light. The lower layer is made of a material containing tantalum and nitrogen and has a thickness of 33 nm or more. The upper layer is made of a material containing tantalum and oxygen and has a thickness of 3 nm or more. The phase difference between the exposure light transmitted through the light-shielding film and the exposure light transmitted in air for a distance equal to the thickness of the light-shielding film is 60 degrees or less.