Disclosed are media recording/reproducing method and device in which recording stop due to over retrials during replacement process and wasteful conversion processing in the recording/reproducing device are suppressed when a method of managing the spare area of a write-once medium by the use of an NAP is employed to manage the spare area of a rewritable medium. During format or replacement process of the medium, the NAP is so updated that defective blocks registered as unusable clusters or as usable cluster type 2 within DFL entries in the spare area are not shown.