A method of manufacturing a mask blank glass substrate or mask blank that includes a mark forming step, and a mask blank glass substrate or mask blank that includes a mark. The mark is a pit formed by irradiating laser light onto a mirror-like surface in an area, having no influence on transfer, on a surface of the mask blank glass substrate. The pit is used as a marker for individually identifying or managing the mask blank glass substrate. The marker may be correlated with information including at least one of substrate information about the mask blank glass substrate, thin film information about the mask pattern thin film, and resist film information about the resist film. A mask blank glass substrate with marker correlated to at least one of the resist film information and thin film information may be used to manufacture a new mask blank.