PURPOSE: To provide a smaller board and a mounting method, which facilitates high-density mounting of many parts by effectively utilizing a space without broadening a mounting area.

CONSTITUTION: A plurality of electrodes 2 and 2' are provided at respective upper and rear surfaces. A connecting terminal 4 linked to each electrode 2 on the upper surface is provided at the side surface. The desired electrodes 2 and 2' at both surfaces are connected to a board by way of a through hole 3 with plating. A board 1A, which has connecting terminals 4A linked to connecting terminals 4 on the side surface and has windows 10, is bonded to the substrate 1 so that the connecting terminals 4 and 4A of both substrates 1 and 1A are linked. The substrate 1A having the windows 10 is attached to a mother board.