A data reading method for a rewritable non-volatile memory module is provided. The method includes performing an error correction decoding operation on an user data stream according to an error checking and correcting (ECC) code to generate a first decoded data stream; searching uncorrectable sub-data units from decoded sub-data units of the first decoded data stream; selecting a target sub-data unit from the uncorrectable sub-data units; adjusting the target sub-data unit in the first decoded data stream to generate an adjusted user data stream; and re-performing the error correction decoding operation on the adjusted user data stream to generate a second decoded data stream; if the second decoded data stream has no error bit, transmitting the second decoded data stream as a corrected data stream to a host system.