A nonvolatile memory device includes memory cells stacked in a direction perpendicular to a substrate and further includes a first memory cell string connected between a selected bit line and a selected string selection line, a second memory cell string connected between the selected bit line and an unselected string selection line, and a third memory cell string connected to an unselected bit line. During a bit line setup section of a program operation, a ground voltage is provided to the selected bit line and a power supply voltage provided to the unselected string selection line is changed to the ground voltage.