A mapping information rebuilding technique for a flash memory is introduced. Mapping information of data that has been stored in the flash memory is recorded in a plurality of logically-grouped tables. System information blocks are provided to store the mapping information by using the logically-grouped table as a management unit. A grouping list is stored in at least one pre-defined physical address of each system information block to list logical group numbers of the logically-grouped tables stored in the physical pages of the corresponding system information blocks. In each system information block, more physical pages are used in storing the logically-grouped tables than are used in storing the grouping list.