A first aspect of the present invention relates to a glass substrate having a content of alkali metal oxides, as represented by molar percentage based on oxides, of 0 to 0.1%, a devitrification-temperature viscosity of 103.2 dPa·s or higher, and an average coefficient of thermal expansion α at 30 to 220° C. of 7.80 to 9.00 (ppm/° C.). A second aspect of the present invention relates to a glass substrate which is to be used for a support substrate for semiconductor packages, the glass substrate having a content of alkali metal oxides, as represented by molar percentage based on oxides, of 0 to 0.1% and a photoelastic constant of 10 to 26 nm/cm/MPa.