To provide a substrate glass for data storage medium which is excellent in weather resistance even when no additional treatment such as chemical reinforcement treatment is applied and less susceptible to a whitening phenomenon and which has a glass transition temperature of at least 680° C. and is excellent in acid resistance.A substrate glass for data storage medium, which comprises, as represented by mass %, from 47 to 60% of SiO2, from 8 to 20% of Al2O3, from 0 to 8% of MgO, from 0 to 6% of CaO, from 1 to 18% of SrO, from 0 to 13% of BaO, from 1 to 6% of TiO2, from 1 to 5% of ZrO2, from 2 to 8% of Na2O and from 1 to 15% of K2O and which has a glass transition temperature of at least 680° C.