An administrative system receives unique ID information of disk from an orderer for ordering manufacture of the disks and provides the unique ID information for a disk maker. The maker stores on the disk unique attribute information of the disk including identification information for the disk maker side. The administrative system obtains normal recording information generated if normal recording is carried out when recording on the disk the unique attribute information of the disk. Alternatively, the administrative system obtains abnormal recording information generated if abnormal recording is carried out. Disk administrative information, for example, number of pieces of the disks delivered from the factory, is generated from the obtained normal and abnormal recording information.