Provided is a memory device including a memory cell array including a normal area in which a plurality of memory cells are arranged, and a redundancy area in which a plurality of redundancy memory cells are arranged, and a repair controller configured to control a repair operation on a defect cell from among the plurality of memory cells according to a first repair unit, and switch a repair unit from the first repair unit to a second repair unit different from the first repair unit when the repair operation based on the first repair unit is completed.