Provided is an image forming apparatus including a temperature sensing circuit to which a temperature sensing element is electrically connected, wherein a surface of a heater on a side where the temperature sensing element is provided is in contact with the inner surface of a film, a heating element is provided in a primary side circuit which is electrically connected to a commercial power supply, and the temperature sensing circuit is electrically insulated from both of the primary side circuit and a secondary side circuit which is electrically insulated from the primary side circuit.