There is a need to improve access speed for a file in a storage system that is provided with multiple storage units having different access speeds.The storage system (10) includes an access frequency acquiring part (14) that divides a past constant accessed data acquisition period into multiple unit periods, and obtains an access frequency for file stored in any of the multiple storage units (30 and 31), a similarity degree calculating part (16) that obtains, for each file, a similarity degree between the access frequency to the file for each unit period, and the access frequency to every other file for each unit period, a grouping process part (17) that groups one or more other files having a similarity degree equal to or higher than a predetermined value, in an identical group, and a file relocation part (18) that places a file belonging to the identical group into a storage unit (30) having a high access speed, when the file stored in the storage units (30 and 31) is accessed and there exists any other file within the identical group to which the file belongs.