Disclosed is an air heating apparatus including an expansion tank that preserves water, a water heater that receives heat from a combustion gas generated through a combustion reaction to heat the water, a heating heat exchanger that receives the water heated by the water heater and exchange heat with air that is to be discharged for heating, a fan that sends the air to the heating heat exchanger, a circulation supply passage that connects the expansion tank, the water heater, and the heating heat exchanger to guide the water in the expansion tank to the heating heat exchanger via the water heater, a circulation recovery passage formed to connect the heating heat exchanger and the expansion tank to guide the water that exchanged heat with the air to the expansion tank, and a hot water heating passage.