When user data fails to be recorded in an address of a user data area, the same data is recorded in an address of a spare area. Information indicating that the data for the address of the user data area is recorded in the address of the spare area is registered in a DL that is loaded in a buffer memory, and the information is recorded in a currently-valid DL area of DMA1. As similar thereto, the information is recorded in a currently-valid DL area of DMA2. If the recording fails, the DL is alternatively recorded in another DL area of the same DMA2. Thereafter, DDSs of DMA2 are deleted, and then, without changing information of the number of times of updating the DDSs, only the staring address of the DL of the DDSs is updated. According to the updating method, it is possible to shorten the time required for updating management information of a medium in an information recording/reproducing apparatus. In addition, it is possible to reduce the number of times of updating management information of an optical disk medium.