A cover glass, containing, by mole percentage: 15 to 40% of P2O5; 15 to 30% of Al2O3; 0 to 15% of SiO2; 0 to 20% of B2O3; 0 to 10% of Li2O; 0 to less than 20% of Na2O; 0 to less than 20% of K2O, provided that Li2O+Na2O+K2O is in a range from 15 to less than 20%; and from 1 to 35% of MgO+CaO+SrO+ZnO. The cover glass being suitable for at least one selected from the group consisting of a solid-state imaging element package and an air-tight sealing of a resin package, and having a sufficient strength not to undergo breakage even when subjected to external force.