PURPOSE: To obtain a low-cost multilayer board which provides an insulation layer with high permittivity, and what is more, excels in heat resistance and reliability by injecting and curing epoxy resin to which an inorganic filler of high permittivity and a curing agent are combined into a cavity formed between printed wiring boards laid out as opposed so that they may not come into contact with each other.

CONSTITUTION: A forming die comprises a top force 1 and a bottom tool 2 and forms a cavity 3. A printed wiring board 4 is laid out in this cavity in such a fashion that its single side may come into contact with the inner surface of the cavity while the other side may not come into contact with each other, forming a cavity 5. A chemical compound, such as titanium dioxide and barium titanate as high permittivity of inorganic filler and epoxy resin to which phenol compound or the like is combined as a curing agent are heated and pressed so that they may fill up the cavity 5 from a spool 6 and cured. After cured, the forming die is opened so that it may be possible to obtain a multilayer foundation 8 having a high permittivity insulation layer 7. Then, they are drilled and a through hole 9 is made where through hole plating is performed.