A computer-implemented method for designing an additively-manufactured object to be built by depositing a plurality of weld bead layers (H1-H7) formed of a weld bead formed by melting and solidifying a filler metal, the method comprising in the following order: an inputting step of inputting a shape data of the additively-manufactured object to a program generating unit; a dividing step of dividing the shape of the additively-manufactured object into a blank region serving as a base body of the additively-manufactured object, and an additive manufacturing region including a protrusion portion to be formed on the base body; and being characterised by: a setting step of setting, as a reference direction, a direction (Vb) in which a sliced layer of the additively-manufactured object is continuously provided and, as a common control section, a section perpendicular to the reference direction (Vb) extended in a circumferential face disposed at a radially central position between an outermost edge of the additively-manufactured object and an outer circumference face of the base body of the additively-manufactured object; a slicing step of slicing the shape of the additively-manufactured object into the weld bead layers (H1-H7) each having a height corresponding to one bead layer (H1-H7) using the data of the shape of the additively-manufactured object, thereby generating the plurality of virtual bead layers; and a bead controlling step of controlling the bead size of each weld bead in association between a change in various welding conditions and a shape of a section perpendicular to the continuous formation direction (Vb) of the weld bead. an inputting step of inputting a shape data of the additively-manufactured object to a program generating unit; a dividing step of dividing the shape of the additively-manufactured object into a blank region serving as a base body of the additively-manufactured object, and an additive manufacturing region including a protrusion portion to be formed on the base body; and being characterised by: a setting step of setting, as a reference direction, a direction (Vb) in which a sliced layer of the additively-manufactured object is continuously provided and, as a common control section, a section perpendicular to the reference direction (Vb) extended in a circumferential face disposed at a radially central position between an outermost edge of the additively-manufactured object and an outer circumference face of the base body of the additively-manufactured object; a slicing step of slicing the shape of the additively-manufactured object into the weld bead layers (H1-H7) each having a height corresponding to one bead layer (H1-H7) using the data of the shape of the additively-manufactured object, thereby generating the plurality of virtual bead layers; and a bead controlling step of controlling the bead size of each weld bead in association between a change in various welding conditions and a shape of a section perpendicular to the continuous formation direction (Vb) of the weld bead. a setting step of setting, as a reference direction, a direction (Vb) in which a sliced layer of the additively-manufactured object is continuously provided and, as a common control section, a section perpendicular to the reference direction (Vb) extended in a circumferential face disposed at a radially central position between an outermost edge of the additively-manufactured object and an outer circumference face of the base body of the additively-manufactured object; a slicing step of slicing the shape of the additively-manufactured object into the weld bead layers (H1-H7) each having a height corresponding to one bead layer (H1-H7) using the data of the shape of the additively-manufactured object, thereby generating the plurality of virtual bead layers; and a bead controlling step of controlling the bead size of each weld bead in association between a change in various welding conditions and a shape of a section perpendicular to the continuous formation direction (Vb) of the weld bead.