A glass substrate contains, as a glass matrix composition as represented by mole percentage based on oxides, SiO2: 58-75%, Al2O3: 4.5-16%, B2O3: 0-6%, MgO: 0-6%, CaO: 0-6%, SrO: 5-20%, BaO: 5-20%, and MgO+CaO+SrO+BaO:15-40%. The glass substrate has an alkali metal oxide content of 0-0.1% as represented by mole percentage based on oxides. The glass substrate has an average coefficient of thermal expansion α of 56-90 (×10−7/° C.) at 50° C.-350° C.