PURPOSE:To prevent snow from being reserved in a duct, by driving a blower only when the detected temperature of the external air is lower than a predetermined value and there is an instruction for operating a cooled body. CONSTITUTION:The blower 2 for blowing air to the cooled body 1 and a blower motor 3 are provided in the duct 4. The set temperature of a temperature detector 7 is 10 deg.C, for example. If the ambient temperature is higher than the set temperature of the detector, electric power C is supplied to drive the blower 2. If the ambient temperature is lower than the set temperature, the electric power C is supplied only when the instruction A is present. If the ambient temperature is lower than the set temperature and the instruction A is not present, the blower 2 is stopped. Therefore, the temperature of the cooled body is not excessively preduced. As a result, the duct does not get clogged with snow.