Abstract: Provided is a nail deformity correction device for effectively correcting a fingernail/toenail by applying an appropriate correction force. The nail deformity correction device includes: a first body having a plate shape, elastically bent by an external force, and being attachable to the surface of a fingernail/toenail; a second body having a plate shape, overlapping the first body, fixed to the first body, and elastically bending with the first body; a core inserted between the first body and the second body and restored into a memorized shape in accordance with a temperature change; and contact portions formed by bringing portions of the first body and the second body in close contact with each other outside the core, in which the first body, the second body, and the core expand and correct a deformed portion of the fingernail/toenail.