A Writter Block Bit Map WBBM is recorded in a lead-in area of a rewritable disc. The WBBM is a bit map that represents whether each block that is a record/reproduction data unit is a recorded block or a non-recorded block. A finalizing process for recording dummy data in the vicinity of a recorded block is performed so that a read-only disc drive can seek a block and a servo operation of the drive can be stable. At this point, with reference to the WBBM, the efficiency of the process can be improved. When a plurality of WBBMs are ring-structured and the WBBMs are successively updated, the write operation can be prevented from being concentrated to the same area. In addition, a destroyed WBBM due to a power failure or the like can be restored. The value of an update counter represents the latest WBBM.