Block management method, memory controller and memory storage device

The invention discloses a block management method for managing an entity block of a rewritable nonvolatile memory and a memory controller and a storage device using the same. The block management method comprises the following steps of: at least grouping the block areas into a data area, an idle area and a replace area; and grouping the entity blocks in the data area and idle area into multiple entity units. The block management method also comprises the following steps of: when an entity block in the entity unit belonging to the data area turns into a bad entity block, extracting an entity block from the entity blocks of the replace area, and replacing the bad entity block with the extracted entity block. The block management method further comprises a step of associating the entity unit without valid data stored therein in the entity units of the idle area with the replace area. According to the invention, the method can effectively utilize the entity blocks and improve the access efficiency.