1. A method for reading data stored in a flash memory, comprising: reading a codeword from a plurality of memory cells; performing a plurality of error correction code (ECC) operation upon the codeword; when the ECC operation succeeds, directly outputting corrected codeword; when the ECC operation fails, performing a plurality of read operations upon each of the plurality of memory cells of the flash memory to obtain a plurality of bit sequences respectively corresponding the memory cells; and determining readout information of the memory cells according to binary digit distribution characteristics of the bit sequences.