NOVELTY - The device (100) has separators whose plate-shaped bottom surface cover portion forms a bottom surface opening between the separators that are adjacent to each other such that a welded part of a tube-shaped heat contraction sheet is guided into the bottom surface opening. The welded part of the heat contraction sheet is arranged in the bottom surface opening when the separators that are adjacent to each other are opposed to each other. Opening width of the bottom surface opening is wider on both side ends than at a center of the bottom surface opening.    USE - Power supply device i.e. battery pack, for use as a large current power supply for an electric motor for driving a vehicle (claimed) e.g. plug-in hybrid vehicle and hybrid electric vehicle such as car. Can also be used as backup power supply devices for signal lights and wireless communication base stations, backup power supply devices installed on a rack of a computer server, backup power supply devices, and as electric power storages for home use and manufacturing plants or street lights connected to solar cells.    ADVANTAGE - The device allows a forcedly-gas-blowing mechanism to forcedly blow cooling gas to gas-flowing paths of the battery block, thus cooling the battery cells of the device in an effective manner. The device increases bearing performance of the separator when the battery block is securely held, and the contact parts of the separator, which are in contact with the battery cell, thus improving heat conduction of the device. The device allows a sealing unit to effectively prevent cooling air from flowing into the gap that is formed by the protruding portion or recessed portion, thus suppressing reduction in cooling performance. The device has a base plate including protruding portions or recessed portions so as to increase stiffness of the device.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a vehicle.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of a power supply device.    Inlet and outlet ducts (41A, 41B)    Fan (42A)    Exterior case (50)    Exterior case portion of exterior case (51)    Power supply device (100)