A battery cooling system includes a cooling fan that takes in inside air of a vehicle cabin to an intake passage and sends the air to a battery communicating with the vehicle cabin through the intake passage, a battery temperature sensor that detects a temperature of the battery, an intake air temperature sensor that is disposed in the intake passage and detects a temperature of the air flowing through the intake passage, and a controller. The controller controls the cooling fan based on the detected temperatures. The controller performs a temperature check operation. Firstly, when the difference value between the detected temperatures is larger than zero, the controller repeats the temperature check operation. Afterward, When the difference value in the latest temperature check operation is smaller than the difference value in the previous temperature check operation and larger than zero, the controller repeats the temperature check operation.