In a temperature regulation device, when a control device determines that warming-up operation of an assembled battery is necessary, and when a humidity of an air detected by a temperature/humidity sensor is equal to or lower than a predetermined humidity, a conditioned air that has been drawn from a vehicle interior and heated is blown to the assembled battery through a battery guide passage. When the humidity of the detected air exceeds the predetermined humidity, an air that has been drawn from a vehicle exterior and heated by a vehicle air conditioning apparatus is blown to the assembled battery through the battery guide passage.