A memory device and a refresh method thereof are provided. The memory device includes a memory array and a controller. The memory array includes a plurality of normal areas and a redundancy area near the plurality of normal areas. The redundancy area includes a plurality of redundancy word lines. A plurality of boundary word lines are arranged near boundaries between the plurality of normal areas and the redundancy area. The controller refreshes the plurality of redundancy word lines in sequence, and refreshes the plurality of boundary word lines in sequence after refreshing the plurality of redundancy word lines in sequence.