NOVELTY - A cooling device for a battery pack (1) including prismatic rechargeable batteries (2) arranged in parallel so that their longer side faces are opposed to each other, where each of the rechargeable batteries has a height larger than a thickness and the longer side faces with a width in a horizontal direction larger than the height comprises a cooling medium path (10) that allows a cooling medium to flow in right and left directions between the longer side faces of the rechargeable batteries; and a cooling medium delivery device (11) that delivers the cooling medium to the cooling medium path.    USE - The cooling device is used for a battery pack as a driving power source for electric vehicles including hybrid cars.    ADVANTAGE - The cooling device efficiently and uniformly cools the individual rechargeable battery. It prevents a decrease in a battery output, charging/discharging efficiency and battery service life.    DETAILED DESCRIPTION - A cooling device for a battery pack including prismatic rechargeable batteries arranged in parallel so that their longer side faces are opposed to each other, where each of the rechargeable batteries has a height larger than a thickness and the longer side faces with a width in a horizontal direction larger than the height, comprises:    (1) a cooling medium path that allows a cooling medium to flow in right and left directions between the longer side faces of the rechargeable batteries; and    (2) a cooling medium delivery device that delivers the cooling medium to the cooling medium path.    The cooling medium path is horizontally formed between the longer side faces of the rechargeable batteries so that the cooling medium flows horizontally through. Each rechargeable battery includes connection terminals provided on both shorter side surfaces of the battery. An upper rib and a lower rib are provided respectively at the upper and lower ends of the longer side faces. The upper and lower ribs extend along the entire length of the longer side faces, to form the cooling medium path.    An INDEPENDENT CLAIM is also included for a rechargeable battery.    DESCRIPTION OF DRAWING(S) - The figure shows a cooling device for a battery pack.    Battery pack (1)    Rechargeable batteries (2)    Cooling medium path (10)    Cooling medium delivery device (11)    Delivery ports (13)    Cooling medium compression transport device (14)