In installing a new virtual machine on one of physical machines, a calculating unit selects an existing virtual machine amongst a plurality of existing virtual machines already deployed on the physical machines based on information about a use form of the new virtual machine and information about a use form of each of the existing virtual machines. The calculating unit predicts a workload on each of the physical machines using history information indicating past workload status of the selected existing virtual machine, and determines an installation-target physical machine for the new virtual machine based on the prediction results.