Provided is a glass composition for a glass fiber, which has excellent alkali resistance, acid resistance, and hydrolytic resistance, is useful as a reinforcing material for composite materials such as calcium silicate board and GRC and as a corrosion-resistant material for battery separators or the like, and has a low glass drawing temperature and liquidus temperature of the glass and thus which is excellent in productivity. The glass composition comprises, in mass % on an oxide base, 50 to 65% of SiO2, 0 to 5% of Al2O3, 0 to 10% of CaO, 10 to 20% of Li2O+Na2O+K2O, 0 to 5% of Li2O, 10 to 20% of Na2O, 0 to 5% of K2O, 5 to 10% of TiO2, and 10 to 20% of ZrO2 as a glass composition.
