A magnesium alloy contains, in atomic percent: 5.7 at. % or more and 8.6 at. % or less of Al; 0.6 at. % or more and 1.7 at. % or less of Ca; 0.05 at. % or more and 0.27 at. % or less of Mn; and 0.02 at. % or more and 0.36 at. % or less of a rare earth element (RE); and any one of 0.1 at. % or more and 0.3 at. % or less of Zn and 0.02 at. % or more and 0.18 at. % or less of Sn, wherein the contents in atomic percent satisfy the condition of the inequality of the following Formula (1), and the balance is Mg and inevitable impurities. (Ca+RE)/Al>0.137  (1)