To disperse the pressure stress to a heating member with a simple and inexpensive structure to attain an extended life of a fixing roller by allowing detection of the position of the fixing roller without providing a special mechanism for detecting the roller position.

In a fixing device comprising a fixing roller 20 including a heating member which is heated by a magnetic flux from an IH coil unit 21, and first and second temperature detection sensors 30 and 31 for detecting a surface temperature of the fixing roller 20, an area (a triangular part 24d in a plan view) in which the temperature is changed by induction heating is set in a non-image area 242b of the fixing roller 20, the surface temperature of the area to which a temperature difference is set is detected by the second temperature detection sensor 31, and the rotating position of the fixing roller 20 is judged based on the temperature difference of the detected surface temperature of the fixing roller 20.