A semiconductor memory device includes a memory cell array, a sense amplifier, and a voltage generator. The memory cell array has a plurality of memory cells. Each of the memory cells is written with "0" or "1" as reference data after "0" or "1" as cell data has been read out from the memory cell. The sense amplifier compares and amplifies the reference data and the cell data read from a memory cell. The voltage generator keeps constant rate of change with time of at least one potential supplied for a read operation for the time interval from readout of the cell data is started until completion of readout of the reference data.