A heating unit heated upon receiving power supplied from an AC power supply, a temperature detecting unit detecting the temperature of the heating unit, a memory storing power energization pattern in which power energization and non-power energization are performed for each percentage of AC power, and a power control unit that determines the percentage of AC power applied to the heating unit based on the temperature and that determines the power energization pattern by referring to the memory are provided. When the power energization percentage is changed, the power control unit changes the power energization pattern after the power energization percentage is changed in accordance with the changed power energization percentage based on the power energization pattern before the power energization percentage is changed and the power energization pattern after the power energization percentage is changed.