A method for manufacturing an annular glass substrate includes: forming, on a glass blank, a separation line that includes a plurality of defects along a predetermined circle by irradiating a surface of the glass blank with a laser beam along the circle; and separating a portion outside the separation line of the glass blank on which the separation line was formed from a portion inside the separation line by heating the portion outside the separation line at a higher temperature than the portion inside the separation line. The separation line includes: a first region in which the defects are periodically formed and an interval between a pair of adjacent defects is a first interval; and a second region in which an interval between a pair of adjacent defects is shorter than the first interval.