To provide a heat pump system controlling the operation of an outdoor fan 7a to improve heating performance when performing heat recovery from an external heat source 12 which is fluctuated regardless of the heat pump system.

A outdoor fan control device 15 finds an outside air heat absorptive temperature Tk in accordance with the quantity of externally supplied heat Q applied by a cooling medium heater 8 so that the outdoor fan 7a is operated when an outside air temperature Tg detected by an outside air temperature sensor 13 is higher than the outside air heat absorptive temperature Tk and the outdoor fan 7a is stopped when the outside air temperature Tg is not higher than the outside air heat absorptive temperature Tk. Thus, the operation of the outdoor fan 7a as blowing means is controlled to improve the heating performance of the heat pump system at all times.