A glass substrate includes a plurality of through holes that penetrate from a first surface to a second surface of the glass substrate. Each through hole has an upper aperture with a first diameter on the first surface and a lower aperture with a second diameter on the second surface. For each of ten through holes selected from the plurality of through holes, a side wall length is obtained from the first and second diameters and the thickness of the glass substrate, and an R value is obtained by dividing the side wall length by the thickness of the glass substrate. The R values fall within a range of 1 to 1.1. A B value, obtained from dividing a difference between the greatest R value and the smallest R value by an average of the R values followed by multiplication with 100, is 5% or less.