A Mg-containing Zn alloy coated steel including a steel and a metallic coating layer placed on a surface of the steel, in which the metallic coating layer is a layered structure of plural flat-form metal particles having a particle diameter of from 5 to 100 μm, and a thickness of from 0.5 to 30 μm, the composition of the metal particles include Zn from 11 to 80 mass %, Al from 3 to 80 mass %, Mg from 8 to 45 mass %, and Ca from 1 to 5 mass %, and the Zn, Al, and Mg content satisfy Zn+Al>Mg, and in which the metal particles include a quasicrystalline phase, an MgZn2 phase, and optionally a balance structure.