The invention solves the problem that data cannot be recorded on a disc because the number of registered Defect Lists (DFLs) has reached a limit and the problem that the access performance is reduced at recording data reproduction time. A cluster, which is normally reproduced during verification processing and is preceded and followed by one or more defective blocks, is also treated as a defective block and, together with the preceding and following defective clusters, recorded in an spare area for extending the range in which clusters are registered as Contiguous Re-allocated Defect (CRD) entries. This reduces the number of DFLs to solve the problem that data cannot be recorded on the disc and, in addition, reduces the number of seek operations to prevent the access performance from being reduced at reproduction time.