There is provided a flash memory device capable of manipulating multi-bit and single-bit data. The flash memory device can include a memory cell array with a plurality of memory blocks. The flash memory device can also include a judgment circuit for storing multi-bit/single-bit information indicating whether each of the memory blocks is a multi-bit memory block or not, determining whether or not a memory block of an inputted block address is a multi-bit memory block according to the stored multi-bit/single-bit information and outputting an appropriate flag signal. A read/write circuit for selectively performing multi-bit and single-bit read/program operations of the memory block corresponding to the block address is also included, as well as control logic for controlling the read/write circuit such that the read/write circuit can perform multi-bit or single-bit read/program operations based on the flag signal. An error checking and correction (ECC) circuit including a multi-bit ECC unit and a single-bit ECC unit for checking and correcting an error in a data of the read/write circuit can also be included.