Provided are a method for producing a polymer molded article, which is capable of increasing crystallinity, heat resistance, and isotropic elastic modulus while maintaining the original shape of a polymer molded body and a polymer molded article obtained by the method and having a high crystallinity, high heat resistance, and a high isotropic elastic modulus. The method for producing a polymer molded article includes the steps of: preparing a polymer material mainly containing a crystalline polymer; and impregnating the polymer material with a first gas having solubility in the crystalline polymer in an atmosphere in which the pressure of the first gas is equal to or higher than atmospheric pressure at a temperature higher than (Tm−30)° C. but lower than (Tm−15)° C., where Tm represents the melting point of the crystalline polymer, to obtain a polymer molded article. The polymer molded article is obtained by such a production method.