There is provided an apparatus and method for executing live-migrations concurrently on a plurality of virtual machines. Resource-usage state information is acquired from each of the plurality of virtual machines when a first live migration of a first virtual machine is started. A correlation factor indicating a degree of correlation between first resource-usage state information for the first virtual machine and second resource-usage state information for each of one or more virtual machines other than the first virtual machine is calculated using the acquired resource-usage state information. Next, a second virtual machine having a positive correlation factor with respect to the first virtual machine is selected from the one or more virtual machines where the positive correlation factor indicating a close similarity between the first and second resource-usage state information. Then, a second live-migration is executed on the second virtual machine in parallel with the ongoing first live migration.