Bad block managing device and bad block managing method

A memory device and a bad block management method thereof are provided to manage data by a unit block according to the information of bad blocks by recording the bad block information in an arbitrary block of the memory device. A storage area comprises a data area(214-2), a preliminary area(214-1) and a table area. Arbitrary data is recorded in the data area. Otherwise, the arbitrary data is recorded in the preliminary area instead of an indicated block, if the indicated block is determined as a bad block. The table area records the bad block address information of the preliminary area and the data area, and the address information of a replacing block of the preliminary area.