To obtain a necessary strength with a simple joining method and enable the automation of lamination and joining by obtaining slice data for each thickness of a metallic plate from a three-dimensional CAD data, cutting and laminating the metallic plate and joining the laminated metallic plates.

The slice data for each thickness of the metal plate are obtd. from the three-dimensional CAD data and the metallic plate is precisely cut. The cut metallic plate are laminated and welding is executed between plates with the same laser beam machine or the other laser beam machines having different performances. In order to prevent the floating up of the thin metallic plate, the joining work is executed while pressurizing it. The laminated metallic plates are joined in order and finally, the difference of step between the metallic plates is removed. The whole thickness of the laminated metallic plates is measured, at each joining of the metallic plates, and the result is fed back to the slice data.