The invention relates to a package board having a core board (30) on each surface of which a plurality of conductor circuits are formed with an interlaminar resin insulating layer therebetween, wherein a plurality of soldering pads (75U,75D) are formed on the IC chip mounted side surface, as well as on the other side surface to be connected to another board, so that said soldering pads (75D) on the other side surface are larger than those on said IC chip side surface of said package board, and a dummy pattern (58M) is formed between conductor circuit patterns formed on said IC chip mounted side surface of said core board.