A cooling device including an intake duct achieving fluid communication between a vehicle interior and an inner part of a battery case, a fan unit for supplying the air via the intake duct to the inner part of the battery case, and a control device is used. The fan unit includes a fan and a motor driven by a constant voltage system. The control device includes a current value detecting portion and a judging portion. The current value detecting portion detects a current value of an electric current supplied to the motor. The judging portion compares the detected current value and a preset reference current value and, when the detected current value is lower than the reference current value, judges that there is an anomaly in a volume of the air supplied to the battery case.