The invention provides a solder alloy for bonding an oxide material, including more than 0% but not more than 1.0% of Mg and the balance being substantially Bi and Sn. Preferably, the alloy includes 0.01 to 0.6% of Mg, 35 to 86% of Bi, and the balance being substantially Sn. The invention can be used for bonding an oxide material, such as bonding glasses to each other. According to the invention, a low-cost solder joint of an oxide material is also provided.