Disclosed herein is a cooling system for vehicle battery packs, which is constructed such that an intake duct for introducing a coolant, such as air, which cools a battery pack, into the battery pack from a predetermined region is not included, air existing inside a vehicle at a region around a battery pack isolated from a cabin of the vehicle is directly introduced into the battery pack, and the air having passed through the battery pack, which has been heated, is discharged through an exhaust duct connected to an internal space of the vehicle, in which a possibility of air to be recirculated to the region around the battery pack is low. The battery pack cooling system according to the present invention uses air existing inside the vehicle. Consequently, the control of temperature and humidity is easier than when external air is used, and generation of noise and backward flow of flames and toxic gas generated during a fire, which are problems caused when the air in the cabin is used, are prevented. Furthermore, it is possible to increase the cooling efficiency of the battery pack without the provision of the intake duct for introducing air into the battery pack.