A method for manufacturing a glass substrate including an opening includes forming an inner circumferential  portion and an outer circumferential portion that are irradiated with a laser
beam along substantially concentric circles in a surface of a glass blank from which the glass substrate is obtained separating a portion on an inner side ofthe outer circumferential  glass blank and a portion on an outer side of the outer circumferential portion from each other by heating the portion on the outer side of the outer  circumferential portion to cause thermal expansion of the portion on the outer side ofthe outer circumferential portion relative to the portion on the
inner side of the outer circumferential portion and form a gap in the outer circumferential portion, and separating a portion on an inner side of the inner circumferential portion of the glass blank
and a portion on an outer side of the inner circumferential portion from each other by heating the portion on the outer side of the inner circumferential portion to cause relative thermal expansion of the portion on the outer side of the inner circumferential portion and form a  the inner circumferential  portion. portion of the gap in