Provided is an inter-volume migration system that allows selection of a relocation-destination volume in consideration of a volume cost. The inter-volume migration system includes a storage subsystem having one or more volumes, an inter-volume relocation instruction module that relocates a data area from a relocation-source volume to a relocation-destination volume, a cost calculation module that calculates a cost value of a volume, and a volume selection module that selects a candidate for the relocation-destination volume based on the cost value of the volume calculated by the cost calculation module and constraints imposed on the relocation-destination volume.