A virtual machine migration method conducted in a virtual machine migration system that includes a virtual machine of a migration source computer and a migrating target computer. The migration source computer conducts processing to send host physical address information of an MMIO region corresponding to a device used by the virtual machine through directed I/O to a migration target computer, and to cause a connection target of the device to be switched to the migration target computer by a switching device that connects the device to the computers. The migration target computer conducts processing to allocate an MMIO region corresponding to the host physical address information sent by the migration source computer, to the device connected to the computers by the switching device.