Provided are a method of writing/reading data into/from a memory cell and a page buffer using different codes for the writing and reading operations. The method of writing/reading data into/from a memory cell that has a plurality of threshold voltage distributions includes a data writing operation and a data reading operation. In the data writing operation, data having a plurality of bits is written into the memory cell by using a plurality of writing codes corresponding to threshold voltage distributions. In the data reading operation, the data having a plurality of bits is read from the memory cell by using reading codes corresponding to the threshold voltage distributions from among the threshold voltage distributions. In the method of writing/reading data into/from a memory cell, a part of the writing codes is different from a corresponding part of the reading codes.