The operating method of the storage device includes receiving write data to be written at the plurality of memory cells; determining whether the received write data is LSB data to be written at the plurality of memory cells; and encoding the write data according to the determination. The write data is encoded according to the write data when the write data is LSB data to be written at the plurality of memory cells. The write data is encoded according to the write data and encoding data of lower data of the write data to be written at the plurality of memory cells when the write data is not LSB data to be written at the plurality of memory cells.