A virtual PCI Express device 1600 indicates the presence of a pseudo I/O device in a PCI Express initial configuration cycle to reserve a resource space for a device anticipated to be installed in the future, and when an I/O device 1400 is inserted into an unoccupied slot 1605, a virtual PCI Express device control logic 1602 notifies a downstream PCI-PCI bridge 1504 via a hot-plugging control line 1601, and the downstream PCI-PCI bridge 1504 generates an interrupt to a CPU 1100 to notify it of insertion of the I/O device 1400 in conformance with the procedure for hot plugging defined by the PCI-SIG Standards, and configuration software 1000 invoked configures the inserted I/O device 1400.