A fixing apparatus includes a heat generating element for generating heat upon electric power supply thereto; a temperature detecting element a for detecting a temperature or the heat generating element; power application control for controlling the power to the heat generating element so that the temperature detected by the temperature detecting element maintains a fixing temperature; and a power setting device for pre-applying power to the heat generating element to detect a rate of temperature change during the pre-application of power, before power is applied to start up the heat generating element to the fixing temperature, and for setting the power to be applied during the start-up period, in accordance with the detected rate of temperature change.