A memory device includes a memory block and a peripheral circuit. The memory block includes a first word line group of word lines included in the memory block and a second word line group of the word lines included in the memory block. The word lines of the first word line group are different from the word lines of the second word line group. The peripheral circuit provides the first word line group and the second word line group with an equalizing voltage during an equalizing section overlapping an erase voltage discharging section for the memory block to constantly keep voltages of the first word line group and the second word line group to the equalizing voltage.