An image forming apparatus includes a heater including a heating element, a driving unit that supplies electrical power to the heating element, and a plurality of temperature detection portions, each detecting a temperature of the heater, and being disposed on a first circuit. A control unit controls the driving unit based on the temperatures detected by the plurality of temperature detection portions, the control unit being disposed on a second circuit, which is isolated from the first circuit. A plurality of abnormality detection circuit portions output signals corresponding to the temperatures detected by the plurality of temperature detection portions, and are disposed on the first circuits. In addition, an abnormality transmission circuit portion transmits a signal indicating an abnormality in the heater to the control unit based on the signals output by the abnormality detection circuit portions.