To be able to transmit a response packet to a target, which is the original request source node, even if, after issuing a request from a node to another, a bus ID/a device ID is replaced in the PCI-Express switch before said another node makes a response to the request source node in a PCI-Express communication system, which uses a PCI-Express switch. For that purpose, a unique node ID for indicating each node is set to the nodes, a channel ID is set to each channel used for data transfer, and the node ID of the transfer destination module, the channel ID of a channel used for the data transfer, and the packet type indicating that the packet is a request or a response are set in an address field of a packet of data transfer. For the data transfer, only a memory write request packet routed by address routing is used.