A memory device comprising: a plurality of memory blocks each including a plurality of word lines arranged between a first and second select line, a peripheral circuit performs an erase operation by applying an erase voltage to a source or drain line of a selected memory block, and a control logic controls, in a period in which the erase operation is performed, the peripheral circuit to: sequentially select the plurality of word lines included in the selected memory block at least one by one from a word line closest to the first and second select line to a word line farthest from the first and second select line, apply a first erase permission voltage to the selected word lines, and apply a second erase permission voltage, which have a higher potential level than the first erase permission voltage, to remaining word lines except the selected word lines.