A file storage control device (for example NAS) comprises a storage space provision portion, which provides, to a higher-level device used by a user, a single storage space associated with a plurality of logical storage units (LUs) provided by a storage system; a reception portion, which receives requests to write files to the provided storage space from the higher-level device; and a storage control portion, which selects a LU from among the plurality of LUs associated with the storage space specified by the write request, and stores all the data constituting the file according to the write request in the selected LU.