A method of surface-treating a metal member involves heating, or heating under pressure, the metal member in an aqueous alkaline solution having a pH of 9 or more and containing a manganese compound and a chelating agent dissolved in water, whereby a mold release agent or dirt is removed from the metal member without any pre-cleaning process. The surface treatment forms on the metal member a surface treatment layer providing excellent corrosion resistance. Paint, which adheres well to the surface treatment layer, can provide additional corrosion protection.