An optical disk of recording type on which data is recordable is provided which includes a data recording and reproducing area (102) for recording data therein and reproducing data therefrom, and a read-only disk identification information area (104) for recording disk identification information (107) for identifying the optical disk therein. In the optical disk, the disk identification information (107) is formed by removing a reflection film formed on the optical disk in a strip shape. The disk identification information (107) includes an inherent disk identifier for each optical disk, and the data recording and reproducing area includes an area for recording therein encrypted data, which is encrypted using information including the disk identification information for identifying the optical disk as a key.