To provide a recording medium having a spare area for defect management and its management information, a method for allocating the spare area, and a method for defect management.

When an initial spare area to be allocated for slipping replacement and linear replacement upon initialization, and a spare area after initialization are not sufficient, a supplementary spare area is allocated. The sizes of the initial and supplementary spare areas are determined according to the number of defects generated upon initialization. Information on the sizes of the spare areas and remainder state information, representing the degree of use of the spare areas, are recorded. This allows the spare areas to be efficiently managed. Moreover, in the defect management method, when an area which has already been replaced linearly is further allocated as a supplementary spare area, defective blocks within the further allocated supplementary spare area are not reapplied for linear replacement, and secondary defect list (SDL) items to the defective blocks are also not changed.