Provided is a crystallizable glass composition which exhibits a high coefficient of thermal expansion after undergoing thermal treatment, has excellent fluidity during the thermal treatment, and is less likely to deteriorate the hermeticity and adhesiveness at bonded portions and volatilize glass components even when exposed to high temperatures for a long period after the thermal treatment. A crystallizable glass composition capable of precipitating MgO-based crystals as main crystals by thermal treatment, the crystallizable glass composition containing, in terms of % by mole in glass component composition, 0.1 to 30% La2O3+Nb2O5+Y2O3+Ta2O5+Yb2O3.