A data managing method, and a memory control circuit unit and a memory storage apparatus using the same are provided. The data managing method including: reading a first data stream from a first physical erasing unit according to a first reading command, wherein the first data stream includes first user data, a first error correcting code and a first error detecting code. The method also includes: using the first error correcting code and error detecting code to decode the first user data and determining whether the first user data is decoded successfully. The method further includes: if the first user data is decoded successfully, transmitting corrected user data obtained by correctly decoding the first user data to the host system in response to the first reading command.