An image forming apparatus includes a processor and heaters which heat a fixing member of an image fixing device. The processor calculates an application pattern for the heaters based on a temperature of the fixing member and generates a drive voltage by suitably selecting half waves from an AC waveform of an AC power supply according to the application pattern. When a duration of time the drive voltage is applied to a first heater in the application pattern having a duty cycle of a predetermined level or less exceeds a predetermined period of time, (i) the processor turns off the first heater and turns on a second heater with a different distribution, or (ii) the processor increases the duty cycle of the first heater and decreases a duty cycle of the second heater.