To provide a nonvolatile semiconductor memory device and its power-up read method.

The nonvolatile semiconductor memory device executes an automatic read operation at a power-up. For the automatic read operation, first, it is detected whether a power supply voltage reaches a first detecting voltage or not at a power-up time. When the power supply voltage reaches the first detecting voltage, it starts to generate a wordline voltage. When the wordline voltage is charged up to a desired voltage level, a read operation of the memory device is executed with a well-known process.