A clad plate for forming an interposer for a semiconductor device which can be manufactured at low cost and has good characteristics, an interposer for a semiconductor device, and a method of manufacturing them. Copper foil materials (19, 24, 33) forming conductive layers (10, 17, 18) and nickel plating (20, 21) forming etching stopper layers (11, 12) are formed and pressed to form a clad plate (34) for forming an interposer for a semiconductor device. Thus, a clad plate (34) for forming an interposer for a semiconductor device is manufactured. The clad plate (34) is selectively etched to form a columnar conductor (17), and an insulating layer (13) is formed on the copper foil material forming a wiring layer (10). A bump (18) for connection of a semiconductor chip and the wiring layer (10) are formed on the opposite side to the side on which the columnar conductor (17) is formed. Thus, an interposer for a semiconductor device is manufactured.