A glass substrate comprising a rectangular glass sheet having a first main surface and a second main surface opposite the first main surface, the glass substrate having a first side and a second side which are adjacent to each other in a view along a thickness direction of the glass sheet, in which a thickness tolerance is less than 6.26 μm in a first cross section which is a cross section in the thickness direction of the glass sheet along a straight line parallel to the first side, the thickness tolerance being a difference between the maximum value and the minimum value of the thickness of the glass sheet.