BATTERY PACK

A battery pack includes a plurality of battery cells (1) and holder (2) that has battery cells (1) arranged in a parallel posture. Holder (2) has partition wall (23) between adjacent battery cells (1) for arranging battery cells (1) at fixed positions. Partition wall (23) has a surface facing battery cells (1) as resin molded layer (12) shaped to arrange battery cells (1) at the fixed positions. Partition wall (23) has a three-layer structure that non-melting plate (13) is disposed inside and resin molded layer (12) is laminated on both surfaces of non-melting plate (13). Holder (2) is formed in a single-piece structure by molding resin molded layer (12) from a synthetic resin.