A main chip has a signal processing circuit for executing signal processing; a plurality of signal transmitting circuits for transmitting signals between the signal processing circuit and a signal transmitting circuit; and a control circuit for controlling operation/non-operation of the signal transmitting circuits in accordance with signal processing content of the signal processing circuit. Functional chips each have a signal processing circuit for executing auxiliary signal processing different from that of the signal processing circuit; and one or a plurality of signal transmitting circuits for transmitting signals between the signal processing circuit and the signal transmitting circuits. The main chip and the functional chips are stacked. The signal transmitting circuits and the signal transmitting circuit are non-contact-type signal transmitting circuits utilizing inductive coupling and are arranged so as to overlap when viewed from the stacking direction.