To provide a heating device capable of properly determining a fault of an on-off valve for circulating/cutting off a flow of a heating medium flowing into a heating terminal provided in a circulation circuit.

A heating device includes a first heating terminal 2 disposed upstream of a circulation circuit 7 and a second heating terminal 3 disposed downstream thereof, an outdoor temperature sensing part 40 for sensing outdoor temperature, an on-off valve 76 communicating/cutting off a flow of a heating medium to the second heating terminal 3, and a heating medium temperature sensing part 45 for sensing the temperature of the heating medium flowing into the on-off valve 76. When a heating operation is started, a determination reference temperature for determining a fault of the on-off valve 76, a determination timing, or a heating medium temperature sensed by the heating medium temperature sensing part 45 is corrected according to the outdoor temperature to determine the fault of the on-off valve 76 using the corrected determination reference temperature or the like.