A memory management method and a storage controller are provided. The method includes performing a decoding operation to a first data stored in a first word line among multiple word lines of a rewritable non-volatile memory module to determine whether the decoding operation is successful or failed, and obtain a first error value of the first word line; when the decoding operation is determined as successful, determining whether to mark the first word line as a bad word line according to the first error value and a first threshold; and when the decoding operation is determined as failed, obtaining a second error value of a second word line adjacent to the first word line, and determining whether to mark both of the first and second word lines as the bad word line according to the first error value, the second error value, and a first threshold.