A memory system includes a nonvolatile memory including a plurality of memory cells, each memory cell being configured to store n levels (n is a natural number of not less than 3) in accordance with a threshold voltage, and a converter which encodes input data in the form of a bit string, records the encoded data in the nonvolatile memory, and limits a difference between levels which adjacent memory cells can take to not more than a predetermined level lower than the n levels.