A nonvolatile memory device includes processing circuitry configured to apply a sub-voltage to the first word lines, determine a desired first read voltage based on a threshold voltage distribution of a plurality of first memory cells connected to the first word lines, apply the sub-voltage to the second word lines, determine a desired second read voltage based on a threshold voltage distribution of a plurality of second memory cells connected to the second word lines, apply the desired first read voltage to the first word lines while simultaneously reading the first memory cells connected to the first word lines, and apply the desired second read voltage different from the desired first read voltage to the second word lines while simultaneously reading the second memory cells connected to the second word lines.