A battery pack that includes a case and a bare cell. The battery pack further includes a screw for combining the case and the bare cell to each other. The screw includes: a head portion having a screw groove formed in a first surface thereof; a body portion disposed on a second surface of the head portion and including a screw thread; and a connection portion disposed between the head portion and the body portion, wherein a thickness of the head portion is within 0.3 to 1 mm.