To provide a cooling structure of a battery pack which is capable of uniformly or efficiently cooling a plurality of battery packs and implementing a simple structure of the same.

In a cooling structure of a battery pack capable of sucking and cooling air using a ventilating fan arranged in a ventilating duct connected to an outlet side in such a manner that the battery for driving a vehicle is arranged in a set cell type which is formed on a plurality of units, a ventilated air collecting chamber 4 is formed behind each ventilating ports 1C and 1D of each set cell 2 and 3 connecting the ventilating duct 4, and one ventilating fan 6 is installed at a lower portion of the ventilating air collecting chamber 4C. A blowing air is uniformly sucked using a plurality of battery packs 2 and 3 and one fan 6 based on the sucking operation of the fan 6 and ventilating air collecting chamber 4C for thereby effectively cooling the battery pack 2 and 3, so that it is possible both to decrease the weight of and to simplify the structure of the apparatus, thus decreasing the fabrication cost.