The nonvolatile semiconductor memory device includes a memory cell array containing a plurality of nonvolatile memory cells and an initial setup data region in which initial setup data specified to determine operation conditions of the device is to be written. The device further includes a detection circuit which detects turn-on of power. The device further includes a readout circuit which reads out the initial setup data from the initial setup data region of the memory cell array upon detecting power-on by the detection circuit. The device further includes a determination circuit which determines whether the initial setup data read out by the readout circuit is effective or ineffective. The device further includes a setup circuit which sets up the device in an operative-prohibiting status when the initial setup data is determined as ineffective by the determination circuit.