A heat treatment method for an additive manufactured object formed of a laminate-molded Ni-base alloy includes: a heat treatment step for carbide precipitation optimization of heating the additive manufactured object for 1 hour or longer and 100 hours or shorter at a temperature which is equal to or higher than a temperature T1 determined by Formula (1) according to amounts of component elements and is equal to or lower than 1,350° C.; and an aging treatment step of heating the additive manufactured object for 1 to 30 hours at a temperature of 800° C. to 950° C. after the heat treatment step for carbide precipitation optimization. T1 (° C.)=177×Ni (%)+176×Co (%)+172×Cr (%)+178×Mo (%)+174×W (%)+171×Al (%)+170×Ti (%)+168×Ta (%)+163×Nb (%)+307×C (%)−16259  (1)