A heating device includes a plurality of chip resistors, a conductor pattern, and a substrate. The plurality of chip resistors generate heat upon receiving power from a power source. The conductor pattern is arranged so as to serially connect the plurality of chip resistors. The conductor pattern is formed on the substrate. The conductor pattern connecting the chip resistors is wider in a forward path from the power source than in a backward path. The majority of the heat generated by the chip resistor is transmitted from the chip resistor to the conductor pattern, and the transmitted heat is radiated from the conductor pattern. Thus, not only the heat from the surface of the chip resistor but also the heat from the conductor pattern serves as heat source.