An object of the present invention is to provide an image fixing apparatus for fixing an image formed on a recording material, which has a heating member, a back-up roller cooperating with the heating member to form a nip therebetween for conveying the recording material, and control device for controlling generation of heat by the heating member, wherein the control device is capable of effecting first control for permitting the heating member to generate heat in a state where an image fixing process is completed and the back-up roller is stopped, and second control for maintaining the heating member at a target temperature, differing from a fixing temperature, during a warm-up period from when the heating member starts to generate heat until the temperature of the heating member reaches the fixing temperature.