Provided is a glass substrate with which it is possible to reduce dielectric loss in high-frequency signals, and which also has excellent thermal shock resistance. This invention satisfies the relation {Young's modulus (GPa)×average thermal expansion coefficient (ppm/° C.) at 50-350° C.}≤300 (GPa·ppm/° C.), wherein the relative dielectric constant at 20° C. and 35 GHz does not exceed 10, and the dielectric dissipation factor at 20° C. and 35 GHz does not exceed 0.006.