NOVELTY - A glass substrate comprises (in %mass) silica (68-81), alumina (0.2-18), boron trioxide (0-3), magnesium oxide (0.2-11), calcium oxide (0-3), strontium oxide (0-3), barium oxide (0-3), zirconia (0-1), sodium oxide (1-18), potassium oxide (0-15), and lithium oxide (0-2). The total content of magnesium oxide, calcium oxide, strontium oxide and barium oxide in glass substrate is 0.2-14 %mass. The glass substrate has glass transition temperature of 500 degrees C or more and average thermal expansion coefficient of 100x 10-7/ degrees C at 50-350 degrees C.    USE - Glass substrate is for copper indium gallium selenide solar cell, cover glass, plasma display panel, inorganic electroluminescent display and thin film transistor panel.    ADVANTAGE - The glass substrate has excellent electric power generation efficiency, flatness, homogeneity and productivity, and high glass transition temperature, and can be manufactured efficiently and economically. The solar cell panel using glass substrate has excellent battery efficiency.    DETAILED DESCRIPTION - A glass substrate comprises (in %mass) silica (68-81), alumina (0.2-18), boron trioxide (0-3), magnesium oxide (0.2-11), calcium oxide (0-3), strontium oxide (0-3), barium oxide (0-3), zirconia (0-1), sodium oxide (1-18), potassium oxide (0-15), and lithium oxide (0-2). The total content of alumina and potassium oxide in glass substrate is 7-27 %mass. The total content of sodium oxide and potassium oxide in glass substrate is 11.5-22 %mass. The total content of magnesium oxide, calcium oxide, strontium oxide and barium oxide in glass substrate is 0.2-14 %mass. The content of magnesium oxide, alumina and potassium oxide in glass substrate satisfies a relation: MgO+0.357Al2O3-0.239K2O-5.58=-3 to 1.5 (I). The content of sodium oxide, alumina and potassium oxide in glass substrate satisfies a relation: Na2O+0.272Al2O3+0.876K2O-16.77=-2.5 to 2.5 (II). The glass substrate has glass transition temperature of 500 degrees C or more and average thermal expansion coefficient of 100x 10-7/ degrees C at 50-350 degrees C. An INDEPENDENT CLAIM is included for manufacture of glass substrate.