A method for manufacturing an additively-manufactured object, includes: an additively-manufacturing step of building a layered body by depositing a weld bead obtained by melting and solidifying a filler metal, the layered body having an opening along a forming direction of the weld bead and an internal space surrounded by the weld bead; and a closing step of forming a closing wall portion connecting an edge portion of the opening with the weld bead for closing. In the additively-manufacturing step, the opening is formed with a width dimension larger than a bead width of the weld bead, and in the closing step, the closing wall portion having a width dimension larger than the bead width is formed by the weld bead to close the opening.