A nonvolatile semiconductor memory device in which a memory cell life can be prolonged while making it possible to perform writing in units of bits. When command information represents writing, a comparing unit 37 compares written data in a target memory cell with write target data to give a comparison result to a write/read control unit 40, when the comparison result represents matching, the write/read control unit 40 does not instruct a decoder unit (51A, 51B, and 53) to perform writing in the target memory cell, and when the comparison result represents mismatching, the write/read control unit 40 instructs the decoder unit to write the write target data in the target memory cell.