A method for producing a metal material involves applying, to the surface of the ZAS alloy, an agent comprising a solvent and, dispersed therein, a material containing Cu such as Cu powder and a Cu—Mn alloy powder and preferably, dispersed or dissolved therein, a reducing agent capable of reducing an oxide film present on the surface of the ZAS alloy, and heating the ZAS alloy having the agent applied thereon, to thereby diffuse Cu into the alloy. The metal material comprises a Zn—Al—Sn based alloy (ZAS alloy) and Cu diffused in the alloy, wherein Cu is diffused into the inside of the alloy to a depth from the surface of 0.5 mm or more, the concentration of Cu decreases from the surface of the ZAS alloy towards the inside thereof, and there is present no specific interface between Cu and the ZAS alloy.