To prevent a fixing roller from being bent and deformed by being pressed by a pressure roller due to that the thickness of the base body of the fixing roller becoming small in order to shorten the start-up time of a fixing device, and its mechanical strength being insufficient.

This device is constituted so that an unfixed developer image formed on the surface of recording paper is thermally fixed by making the recording paper pass through a press-contact position between a fixing roller 1 driven to be rotated and the pressure roller 2 rotated in press-contact with the roller 1. In this case, the roller 1 is a fixing roller equipped with the cylindrical base substance 1B and a heating resistor layer 1D formed on the surface of the base body 1B through an insulating layer 1C and energized to generate heat, and a rotatable cleaning member 3, consisting of a roller-like elastic member 32 whose outside diameter is increased by thermal expansion, is arranged at a prescribed position facing opposite the press-contact position of the roller 2 for pressurizing the roller 1 in a state where it abuts on the roller 1.