Provided is a battery temperature control device configured to automatically heat a battery with a battery-driven heater so that the battery does not freeze at a minimum electric power consumption when the battery is out of use. The battery temperature control device predicts, based on a combination of a battery temperature and an outside air temperature, a predictive time that the battery temperature is likely to be less than a first set temperature, while the battery temperature is higher than or equal to the first set temperature at which there is no risk of freezing, and sets the predictive time as the next controller startup time, and determines whether or not the battery temperature has fallen to below the first set temperature with a control program wakeup when the predictive time has expired, and battery-drives the heater when the battery temperature fall has occurred, to heat the battery.