To prevent a decrease in a capacity of a heat exchanger by allowing a gradient of a fan to follow up a wind direction of a natural wind and stably holding a supply air amount to a heat transfer unit in an air cooled heat exchanger for a thermal power or nuclear reactor power plant.

A rotary shaft 5 is provided perpendicularly to a fan shaft 4 between an outer peripheral side of a casing 2 of an axial fan 1 and a trestle 3 of the heat exchanger to hold the entire fan. A beam 7 is laterally bridged between a discharge side of the casing 2 and a lower side of a heat transfer unit 6. An expansion 8 is mounted between a lower surface of the beam 7 and a discharge port of the casing. When a natural wind is weak, the wind is normally forced by the forced power of the fan 1, while when the wind is strong, the entire fan 4 is inclined to forcibly supply the wind.