A method for manufacturing a glass substrate including an opening includes forming lines of inner and outer circumferential portions irradiated with a laser beam along substantially concentric circles in a surface of a glass blank, separating a portion on an inner side of the line of the outer circumferential portion of the glass blank and a portion on an outer side of the line of the outer circumferential portion from each other by heating the portion on the outer side of the line of the outer circumferential portion with radiant heat, and separating a portion on an inner side of the line of the inner circumferential portion of the glass blank and a portion on an outer side of the line of the inner circumferential portion from each other by heating the portion on the outer side of the line of the inner circumferential portion with radiant heat.