Cross bar control circuits are connected to each other by two buses, which are a broadcast bus for transmitting a broadcast packet from a system board to all system boards other than the system board and a point-to-point bus for transmitting a unicast packet from a system board to another system board. When unicast packets passing through the point-to-point bus are too many, the unicast packets are output by using the broadcast bus in addition to the point-to-point bus if the broadcast bus is not used. In this way, the unicast packets can be output quickly and efficiently, so that use efficiency of the broadcast bus and the point-to-point bus can be increased as a whole.