The invention provides a memory apparatus including a memory cell array and a hierarchical error correction code (ECC) layer. The hierarchical ECC layer, includes N layers of ECC coder-decoder, wherein the hierarchical ECC layer enables one of the N layers to operate an encoding or decoding operation on processed data, and the hierarchical ECC layer enables another one of the N layers merely when the error bit number of the processed data reaches to N−1 pre-set error correction number(s), and N is a positive integer larger than 1.