The inventive concept relates to a nonvolatile memory device and methods for operating the same. The nonvolatile memory device comprises a plurality of strings arranged in rows and columns on a substrate, each string including at least one ground select transistor, a plurality of memory cells and at least one string select transistor sequentially stacked on the substrate. The method comprises erasing first memory cells corresponding to an erasure failed row and inhibiting erasure of second memory cells corresponding to an erasure passed row, and performing an erasure verification by a unit of each row with respect to the first memory cells.