A battery unit for vehicles comprises a plurality of battery, bus bars, and insulating plates. The plurality of batteries is installed with the terminals facing in the same direction, where the direction to which the pairs of terminals are facing is arranged in the same direction and the batteries are electrically connected by the bus bars. A refrigerant flows in the direction to which the pairs of terminals are connected, and cools the terminals and the bus bars. The insulating plates are disposed between the bus bars connected with different batteries. In addition, the insulating plates and are disposed extending in the direction to which the pairs of terminals are connected.