A battery pack includes a plurality of battery stacks integrated by stacking a plurality of unit batteries, a fluid passage where fluid flows for cooling the unit batteries disposed between the battery stacks, a blower for circulating the fluid in the fluid passage, and a plurality of heat conducting plates. The heat conducting plate is thermally connected to an outer casing of the unit batteries constituting the battery stacks adjacent to each other, and disposed so as to constitute a plurality of cooled portions of which parts thereof exist in the fluid passage. The battery pack includes a passage forming member that demarcates the fluid passage as an independent passage from the area near the outer casing of the unit battery, and includes a partition wall for supporting the heat conducting plate.