In a fixing device, a fixing unit fixes a toner image transferred onto a recording medium by a heating target unit heated by a plurality of heating units each of which is grouped as a first heating unit to which power is selectively supplied or a second heating unit to which power is supplied in priority to the first heating unit, and a supply control unit supplies power to a heating unit grouped as the second heating unit and selectively supplies power to a heating unit grouped as the first heating unit, among the heating units that heat the heating target unit of which detected temperature by a detecting unit is lower than a target temperature.