A nonvolatile memory device includes: a plurality of cell strings disposed on a substrate, wherein at least one of the plurality of cell strings comprises a plurality of cell transistors and at least one ground select transistor stacked in a direction substantially perpendicular to the substrate, and the substrate and a channel region of the plurality of cell strings have a same conductivity type; a substrate bias circuit configured to provide an erase voltage to the substrate in an erase operation; and a ground select line voltage generator configured to provide a ground select line saturation voltage to the at least one ground select transistor in the erase operation.