A plurality of module substrates have circuit boards, respectively. The circuit boards are stacked with a space therebetween, and are connected to first end portions of connecting members. The second end portions of the connecting members are connected to connecting pads disposed on a motherboard. The module substrates are thus stacked and mounted on the motherboard so as to increase the mounting density. By causing the connecting members for the upper circuit board to project further than the connecting members for the lower circuit board, the connecting members for the upper and lower circuit boards are prevented from touching each other.