In a method of erasing data in a nonvolatile memory device including a memory block, it is determined whether a data erase characteristic for the memory block is degraded for each predetermined cycle. The memory block has a plurality of memory cells therein, the plurality of memory cells being stacked in a vertical direction relative to an underlying substrate. A data erase operation is performed by changing a level of a voltage applied to selection transistors for selecting the memory block as an erase target block when it is determined that the data erase characteristic is degraded.