A memory device includes: a first casing; a second casing on the first casing; a memory module in an inner space between the first and second casings; and a plate between the first and second casings, wherein the plate includes an air hole and a wing, and wherein the wing includes: a first segment near an outside of the first and second casings; and a second segment near the inner space, wherein the first segment is located at a level different from a level of the second segment.