Memory system and wear-leveling method thereof

A memory system includes a memory device performing write operations on lines included in a memory block among a plurality of memory blocks included in the memory device; a counting unit counting a write count for each of the plurality of memory blocks, and outputting the write counts; a first wear-leveling unit performing a wear leveling operation by shifting the lines of each of the plurality of memory blocks; and a second wear-leveling unit detecting hot and cold memory blocks among the plurality of memory blocks based on the write counts, and swapping the hot memory block with the cold memory block, wherein the second wear-leveling unit selects at least one memory block among the plurality of memory blocks based on the write counts, and checks whether the write operation is performed on each of the lines included in the selected memory block.