A method for manufacturing an additively-manufactured object in which deposition is performed by melting and solidifying a metal depending on three-dimensional shape data of a target shape, the method comprising: acquiring the three-dimensional shape data; creating a deposition plan in which a formation track in which each layer obtained by slicing a shape of the three-dimensional shape data is formed by the metal and a heating condition of the metal are determined; the method being characterised by the following steps: determining a difference between a shape of the additively-manufactured object that thermally contracts by cooling after deposition and a shape of the three-dimensional shape data by an operation in a case where the additively-manufactured object is built by the deposition plan, wherein determining the difference by an operation includes analytically determining a deformation amount (ΔL) due to the thermal contraction occurring in the additively-manufactured object, and determining a difference (Δd) from a shape model having the shape of the three-dimensional shape data; obtaining a modification shape model by modifying the shape model using the deformation amount (ΔL) so that the shape of the additively-manufactured object after additive manufacturing and thermal contraction becomes the shape of the shape model; modifying the deposition plan by using the modification shape model, wherein the formation track and the heating condition are changed; analytically determining the deformation amount (ΔL) generated in the additively-manufactured object when additive manufacturing is performed by the modified deposition plan; determining the difference Δd between the shape of the additively-manufactured object deformed by the analytically determined deformation amount (ΔL) and the shape model; repeating the steps of obtaining a modification shape model, modifying the deposition plan, analytically determining the deformation amount (ΔL), and determining the difference (Δd) if the difference (Δd) does not fall within a predetermined allowable range (ε) until the difference (Δd) falls within the predetermined allowable range (ε); and additively manufacturing the additively-manufactured object based on the modified deposition plan in which the difference (Δd) falls within the predetermined allowable range (ε). acquiring the three-dimensional shape data; creating a deposition plan in which a formation track in which each layer obtained by slicing a shape of the three-dimensional shape data is formed by the metal and a heating condition of the metal are determined; the method being characterised by the following steps: determining a difference between a shape of the additively-manufactured object that thermally contracts by cooling after deposition and a shape of the three-dimensional shape data by an operation in a case where the additively-manufactured object is built by the deposition plan, wherein determining the difference by an operation includes analytically determining a deformation amount (ΔL) due to the thermal contraction occurring in the additively-manufactured object, and determining a difference (Δd) from a shape model having the shape of the three-dimensional shape data; obtaining a modification shape model by modifying the shape model using the deformation amount (ΔL) so that the shape of the additively-manufactured object after additive manufacturing and thermal contraction becomes the shape of the shape model; modifying the deposition plan by using the modification shape model, wherein the formation track and the heating condition are changed; analytically determining the deformation amount (ΔL) generated in the additively-manufactured object when additive manufacturing is performed by the modified deposition plan; determining the difference Δd between the shape of the additively-manufactured object deformed by the analytically determined deformation amount (ΔL) and the shape model; repeating the steps of obtaining a modification shape model, modifying the deposition plan, analytically determining the deformation amount (ΔL), and determining the difference (Δd) if the difference (Δd) does not fall within a predetermined allowable range (ε) until the difference (Δd) falls within the predetermined allowable range (ε); and additively manufacturing the additively-manufactured object based on the modified deposition plan in which the difference (Δd) falls within the predetermined allowable range (ε).