Provided is a heat treatment method that is implemented on an additive manufactured object formed from a laminate Ni-base alloy, wherein the method has a carbide deposition optimization heat treatment step wherein the additive manufactured object is heated for 1 – 100 hours at a temperature greater than or equal to T1 according to Equation (1) in correspondence with the amount of each component element and less than or equal to 1350°C, and thereafter an aging treatment step with heating for 1 – 30 hours at a temperature in a range of 800 – 950°C. T1 (°C) = 177 × Ni (%) + 176 × Co (%) + 172 × Cr (%) +178 × Mo (%) + 174 × W (%) + 171 × Al (%) + 170 × Ti (%) + 168 × Ta (%) + 163 × Nb (%) + 307 × C (%) − 16259 … (1)
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