1. A semiconductor device manufacturing method; comprising:preparing a multilayer board and a plurality of contact parts, the multilayer board including an insulating layer; a circuit pattern layer formed on a front surface of the insulating layer, and a metal layer formed on a rear surface of the insulating layer and having an area larger than an area of the circuit pattern layer in a plan view of the multilayer board;
arranging each of the plurality of contact parts on the circuit pattern layer of the multilayer board via a bonding material;
arranging a pressing area of a main surface of a plate-shaped holding jig on the plurality of contact parts; and
while heating the multilayer board, pressing the plurality of contact parts against the multilayer board by inclining the pressing area of the holding jig to conform to a warp of the multilayer board.