A Zn—Al—Mg-based plated steel sheet has, an alloy layer formed on a surface of a steel sheet and contains Fe and Si, and a plated layer formed on a surface of the alloy layer opposite to the steel sheet, in which the plated layer and the alloy layer include, in mass %, Al: 45.0 to 65.0%, Si: 0.50 to 5.00%, Mg: 1.00 to 10.00%, and a balance of Zn, Fe, and impurities, the plated layer contains 0.1 to 20.0% of a Mg—Si phase in terms of volume fraction, an average equivalent circle diameter of the Mg—Si phase in the surface layer area is 0.1 to 15.0 μm, and an integrated value of a Si content from the surface to thickness center of the plated layer is 0.55 times or more of an integrated value of the Si content from the surface to an interface.