In the case where a spare area management method using an NAP of a spare area on a recordable medium is applied to a spare area management method of a spare area on a rewritable medium, in order to alleviate a recording stop caused by retry over in a replacement process or unnecessary conversion processes in a record/reproduce device, the NAP is updated in a format process or in the replacement process in such a way as to avoid defective blocks within the spare area which is registered as Unusable Cluster or Usable Cluster Type 2 entries on the DFL.