A fixing apparatus allows harmonic noise and flicker noise caused by alternating current to be reduced. To accomplish this, the fixing apparatus has a power supply unit that supplies AC power from a commercial power supply to a heater, a temperature detection element that detects the temperature of the heater, a setting unit that sets a duty ratio for providing power to the heater such that the temperature detected by the temperature detection element maintains a target temperature, and a control unit that controls the power supply unit such that an average power duty ratio of a single cycle equals the power duty ratio based on the detected temperature, where a single cycle is three or more full waves of the commercial power supply, there being three or more power duty ratios per one half wave of the commercial power supply in a single cycle.