A file storage apparatus comprises: duplication determination unit that determines whether file supplied from client apparatus and file stored in storage unit coincide with each other in same format, and stores the file supplied from client apparatus in the storage unit if the files do not coincide in the same format; and storage management unit that associates, if duplication determination unit determines that the files coincide in the same format, format of the file supplied from the client apparatus with the file stored in the storage unit, reads file stored in the storage unit in response to file read request from client apparatus, converts, if format associated with the read file exists, the read file into the format, and provides the converted file.