A heating device including a main power source; a sub power source including a capacitor capable of charging and discharging; a heating member including a main heater and an auxiliary heater and configured to heat a material with the heater and the auxiliary heater, wherein the main heater and the auxiliary heater are supplied with electric power by the main power source and the sub power source; and a sub power source controller configured to control the sub power source such that a temperature of the auxiliary heater is controlled so as to be a target temperature, wherein the sub power source controller changes the target temperature, if necessary. A fixing device and an image forming apparatus including the heating device are also provided.