A method of erasing a non-volatile memory device which includes a plurality of NAND strings is provided as follows. A first voltage is applied to each of word lines for a corresponding effective erasing execution time. An erase operation is performed on memory cells connected to each of the word lines for the corresponding effective erasing execution time. A second voltage is applied to each of at least some word lines among the word lines for a corresponding erasing-prohibited time after the corresponding effective erasing execution time elapses. A sum of the corresponding effective erasing execution time and the corresponding erasing-prohibited time for each of the at least some word lines is substantially equal to an erasure interval during which an erase operation is performed using the first voltage and the second voltage higher than the first voltage. The word lines are stacked on a substrate.