An error correcting method for a memory chip is provided. The memory chip has a plurality of physical blocks, each of the physical blocks has a plurality of physical pages, and the physical pages belonging to the same physical block are individually written and simultaneously erased. The error correcting method includes sequentially writing a plurality of data into the physical pages of a first physical block and generating a parity information according to the data. The error correcting method further includes writing the parity information into one of the physical pages of the first physical block following the data and correcting the data in the first physical block according to the parity information. Accordingly, the parity information can be used for correcting error bits in the data when an error checking and correcting circuit can not correct the error bits. Thereby, the error correcting ability is enhanced.