A cooling system for cooling a main battery 10 includes a cooling fan 40 and a temperature sensor 61 configured to detect a battery temperature TB. The cooling system performs constant control in which the cooling fan 40 is driven at a constant command value when the battery temperature TB reaches or exceeds a first temperature T0 after startup of the electrically powered vehicle. Additionally, the cooling system detects whether or not a malfunction occurs in the cooling fan 40, based on an actual rpm of the cooling fan 40 obtained during the constant control. The cooling system performs the constant control in a situation in which charging of the main battery 10 is continued for a predetermined period of time or longer after the startup of the vehicle, regardless of whether the battery temperature TB is below the first temperature T0.