Disclosed is a battery pack including guide recesses inside a case. The battery pack includes a core pack including a bare cell, and a protective circuit member electrically connected to the bare cell, a case accommodating the core pack, and an upper cover covering the core pack. The case includes a base plate, reinforcement plates vertically extending from edges of the base plate, and a resin part surrounding the reinforcement plates. A guide recess is disposed inside the resin part.