Apparatus and method for saving and managing additional data of file system

A device and a method for storing/managing additional data in a file system are provided to store additional information by using an unused area for file information of a directory entry without degrading compatibility of an FAT(File Allocation Table) file system to increase performance of the FAT file system. A searcher(310) searches an area where the information of a file stored in the directory entry is not used. A storing part(330) stores the additional information to the searched area. An additional information manager(360) locates the additional information by using signature and a checksum of the stored additional information. If it is determined that the checked entry is an empty area by checking whether the directory entry before or after the directory entry in a used state is empty, the additional information manager checks whether the signature for the additional information exists in the empty area, and checks a changed state of the checksum of the information if the signature exists. If the checksum is not changed, the additional information manager determines that the added information is found.