An optical recording medium record/playback apparatus manages defective areas in a rewritable optical recording medium. A linear replacement control (LRC) bit is added to a secondary defective list (SDL) entry to discriminate defective block information listed in the SDL entry, according to a linear replacement algorithm, from defective block information listed at the SDL entry, according to a skipping algorithm. This allows the apparatus to transmit correct information to a host. When a defective block requiring a new replacement block is found during recording or playing back data and the spare area is full, instead of carrying out the linear replacement, the LRC bit is set in the SDL entry, along with the location information of the defective block. This indicates that the SDL entry was made when the spare area was full. Thus, data is not written in, or read from, the defective block.