A plurality of multi-layer metal plates (1) each being composed of a bump forming metal layer (2), an etching stop layer (3), and a wiring film forming metal layer (4), and in which a wiring film (4a) is formed from the wiring film forming metal layer and a bump 2a is formed from the bump forming metal layer are prepared, and on a bump forming surface of a multi-layer metal plate, a wiring film of another multi-layer metal plate is overlapped. Such lamination process is repeated in succession for multi-layering. In addition, a polishing machine for multi-layer wiring board (11a) which includes metal plate holding means (13) for holding a metal plate (1a), cutter holding means (25) for holding a cutter (26) above the metal plate, height adjustment mechanism (20) for adjusting the height of the cutter holding means, and cutter parallel moving mechanism (15) for relatively moving the cutter holding means in parallel to the surface of the metal plate is used to conduct polishing.