In terms of mass%, 0.95 to 2.00% Zn, 0.05% to less than 0.30% Zr, 0.05 to 0.20% Mn are contained, and the balance is Mg and inevitable impurities. And a magnesium alloy having an average crystal grain size of 1.0 to 3.0 μm and a grain size standard deviation of 0.7 or less. 質量%で、0.95~2.00%のZn、0.05%以上0.30%未満のZr、0.05~0.20%のMnを含有し、残部がMgおよび不可避的不純物からなり、平均結晶粒径が1.0~3.0μm、粒径の標準偏差が0.7以下の粒径分布を有するマグネシウム合金。