In a system including a plurality of physical machines to execute virtual machines (VM1, VM2), migration virtual machine information and definition information are saved in a physical machine executing a virtual machine (VM1) to be migrated and a storage of a physical machine as a migration destination. During the migration of the virtual machine, machine identification information of a migration partner, unique information assigned to the virtual machine, and information indicating whether the physical machine executing the processing is a migration-source or migration-destination physical machine are saved in a migration information storage area. A migration recovery section examines information stored in a definition information storage area and a migration information storage area to determine a recovery procedure to restore the virtual machine.