In one embodiment, in a standby mode, an endless heating belt is caused to move apart from a hot roller. Furthermore, in color mode, the endless heating belt is caused to contact the hot roller to make possible thermal conduction between the endless heating belt and the hot roller, and a surface temperature of the endless heating belt is adjusted within a prescribed range of 200° C. to 210° C. being higher than a fixing temperature of 180° C. Further still, in monochrome mode, a length (or a surface area) of a heating contact region between the endless heating belt and the hot roller is set to a maximum to increase a thermal conduction efficiency between the endless heating belt and the hot roller, and a surface temperature of the endless heating belt is adjusted within a prescribed range of 210° C. to 220° C. being sufficiently higher than the fixing temperature of 180° C.