A printed circuit board assembly has plural printed circuit boards that are mechanically and electrically connected to each other with them being stacked, and a connection layer that connects the adjacent two printed circuit boards to each other is provided. The connection layer includes an insulation portion and an electric conduction portion. The insulation portion contains an insulating member and is adhered to each of the adjacent two printed circuit boards. The electric conduction portion passes through the insulation portion and connects electrode terminals of the adjacent two printed circuit boards.