a base driving step of a base drive moving a base in a downward direction by a predetermined distance;

a raw material supply step of a raw material supply device supplying raw material powder to a powder container with an iron alloy product being present in the powder container;

a forming step of laminating and forming iron alloy layers on the base, by irradiating the raw material powder of the iron alloy with either a laser beam or an electron beam and melting the raw material powder;

a first temperature control step of, during execution of the forming step, controlling an iron alloy layer temperature T1° C. of a predetermined number of laminated layers from a surface layer of the iron alloy layers formed in the forming step such that the iron alloy layer temperature T1° C. is kept within a range of Ms ° C.≤T1° C.≤Ms ° C.+α where Ms ° C. is a martensitic transformation start temperature and a is a predetermined value; and

a second temperature control step of, during execution of the forming step, controlling a temperature T2° C. of the base such that the temperature T2° C. of the base is kept within a range of Mf ° C. β≤T2° C.≤Mf ° C. where Mf ° C. is a martensitic transformation finish temperature and β is a predetermined value, wherein

the first temperature control step and the second temperature control step are executed simultaneously during execution of the forming step at a timing at which the iron alloy layers are laminated on an upper surface of the iron alloy product.