A first semiconductor chip includes a first inductor and a second inductor, and a second semiconductor chip includes a third inductor and a fourth inductor. The first inductor is connected to a first receiving circuit of the first semiconductor chip, and the second inductor is connected to a second transmitting circuit of the second semiconductor chip through a first bonding wire. The third inductor is connected to a second receiving circuit of the second semiconductor chip, and the fourth inductor is connected to a first transmitting circuit of the first semiconductor chip through a second bonding wire.