HEAT FIXING DEVICE

PROBLEM TO BE SOLVED: To provide a heat fixing device which can improve print precision by holding a pressure roller in a proper rotating state and prevent an abnormal image from being formed. SOLUTION: The heat fixing device which has a means having a conductive layer between a base layer and a surface layer and applying a bias voltage to the conductive layer and a circuit for grounding from a contact member in contact with the conductive layer through a resistance, is equipped with a heat-resisting film driven by a pressure roller, a heating body, a heat-resisting support member supporting the heating body, and the pressure roller, clamps and carries a recording material carrying an electrostatically formed toner image by the heat-resisting film and the pressure roller arranged while pressed against the heating body across the heat-resisting film, and heats and presses the recording material and toner image to fix the toner image on the recording material detects the voltage across the resistance and detects the heat-resisting film rotating according to the detection result, thereby controlling the heat fixing device according to the detection result.