Abstract: Disclosed are an apparatus and a method for storing and managing additional data in a file system. The apparatus comprises a search unit to search for an unused region in a directory entry, a storage unit to store additional data in the unused region, and an additional data managing unit to locate the position of the additional data using the signature and checksum of the additional data. The method includes (a) searching for an unused region of a directory entry, (b) storing additional data in the unused region, and (c) locating the position of the additional data using the signature and checksum of the additional data. According to the present invention, additional data can be stored, used and managed utilizing unused regions of a directory entry without degrading the compatibility of the file system, and enhancing the performance of the FAT file system.