In a battery cooling structure, a battery case housing a large number of battery modules is formed into the shape of a rectangular tube having a cooling air inlet and a cooling air outlet, and V-shaped cooling air guide channels having a decreasing flow-path cross sectional area are provided on inner faces of air guide plates that define upper and lower faces of the rectangular tube. The flow of cooling air is deflected by these V-shaped cooling air guide channels toward a central part on the downstream side, thus effectively cooling the battery modules disposed in the central part, for which the cooling effect is poor to make uniform the temperature of the battery modules, resulting in a suppressed variation in capacity and lifetime. Moreover, since it is not necessary to provide a bypass passage in the battery case, it is possible to simplify the structure of the battery case, reduce the dimensions, and improve the degree of freedom in the layout.