A method for heat-treating a metal molded article, the method including a shape holding layer formation step for treating a metal molded article so that a shape holding layer having a melting point higher than the solidus temperature Ts of a structure of the metal molded article is formed on the surface of the metal molded article, and a first heat treatment step for performing a first heat treatment at a first temperature T1 on the metal molded article after the shape holding layer is formed by the shape holding layer formation step, the shape holding layer formation step and the first heat treatment step being performed so as to satisfy the expression Ta < T1 < Tm, where Ta is a reference temperature 100 DEG C lower than the solidus temperature Ts, and Tm is the melting point of the shape holding layer.