A nonvolatile semiconductor memory device can carry out a forming process simultaneously on the nonvolatile variable resistive elements of memory cells and make the forming time shorter. The nonvolatile semiconductor memory device has a forming detection circuit provided between the memory cell array and the second selection line (bit line) decoder. The forming detection circuit detects the completion of the forming process for memory cells by measuring the fluctuation in the potential of second selection lines or the current flowing through the second selection lines when applying a voltage pulse for a forming process through the second selection lines simultaneously to the memory cells on which a forming process is to be carried out connected to the same first selection line (word line), and prevents a voltage from being applied to the second selection lines connected to the memory cells where the completion of the forming process is detected.