Abstract: After preparing a plurality of flat plate material members by compressing material powder, a region of an initial flat plate material member corresponding to a designed cross sectional shape is irradiated with irradiated light (laser light) L, to form an initial cross sectional element that is hardened after being melted. The surface of the initial cross sectional element is then leveled. Next, the next flat plate material member is arranged on the surface of an already manufactured section having a leveled one side surface. Irradiated light is then irradiated to a region of the new flat plate material member corresponding to the designed cross sectional shape at the layer position of the new flat plate material member, and a layer cross sectional member is formed by hardening after melting, and integrated with an already formed section. The surface of the layered cross sectional element is then leveled.