A free cooling outdoor unit includes: a refrigerant circuit through which refrigerant circulates; a brine circuit through which brine circulates; a water circuit through which water circulates; a fan configured to send air to the second heat exchanger; a flow control valve configured to control a circulation amount of the brine in the brine circuit; a water temperature detection sensor configured to detect a water temperature in the water circuit; an outside air temperature sensor; and a controller configured to control, where the outside air temperature is equal to or lower than a freezing temperature of the brine, the circulation amount of the brine based on the water temperature such that a brine temperature is prevented from reaching a temperature equal to or lower than the freezing temperature of the brine.