A heating unit includes a board including metal, an insulating layer including insulating material and formed on a surface of the board, a heating element disposed on the insulating layer to generate heat by passing an electric current through the heating element, and a conductive portion electrically connecting the heating element and the board to each other. The heating unit further includes a first power supplying electrode electrically connected to the heating element and a second power supplying electrode electrically connected to the board. The heating element, the conductive portion and the board constitute an electric circuit between the first power supplying electrode and the second power supplying electrode. The heating element generates the heat in a case where the first power supplying electrode and the second power supplying electrode are electrically connected to a power source and the electric current is passed through the electric circuit.