1. A data managing method for managing a data managing device, the data managing device including a plurality of storage devices arranged to store files, and the data managing device managing both a table for managing the files and the files, the data managing method comprising the steps of: storing, in both a folder information managing table and a file information managing table, information used for displaying a logical structure; storing, in a reference path information managing table, a reference path ID indicating a storage position of each of the files; storing, in a storage destination changing condition managing table, information regarding a storage destination changing condition associated with each of the reference path information; acquiring, from the reference path information managing table, and in response to an instruction for changing a storage destination of a file, a reference path ID corresponding to the file for which the storage destination changing condition has been changed; acquiring, from the storage destination changing condition managing table, the storage destination changing condition; acquiring information regarding whether a storage destination change can be made for each of the reference paths respectively corresponding to each of the reference path ID from the storage destination change condition managing table; examining whether the file for which the storage destination condition has been designated fulfills the file storage destination changing condition at a preceding access date for the file; moving the file to a physical destination of a storage device corresponding to the file storage destination changing condition when the storage destination condition fulfills the file storage destination changing condition; and designating the reference path ID in the storage destination change condition management table to a reference path in the storage device to which the file has been moved.