In a stacked chip system, an IO circuit connected to a TSV pad for IO and a switch circuit constitute an IO channel in each chip, the IO channels as many as the maximum scheduled number of stacks are coupled together and connected to constitute an IO group, and the chip has one or more such IO groups. Each TSV pad for IO is connected with a through via to an IO terminal at the same position in a chip of another layer. On an interposer, if the actual number of stacks is less than the maximum scheduled number of stacks, connection pads for IO in adjacent IO groups on the interposer are connected via a conductor.