Conventionally, there is a multi function peripheral (hereinafter referred to as an “MFP”) and an image forming apparatus such as a printer and the like. The image forming apparatus is provided with a fixing device. The fixing device heats a fixing belt through an electromagnetic induction heating method (hereinafter referred to as an “IH method”) to fix a toner image on an image receiving medium through the heat of the fixing belt. The fixing belt has a heating layer which generates heat through induction current. The fixing device reduces the heat capacity of the fixing belt to reduce the warming up time and the like. The fixing device includes a magnetic shunt alloy layer for compensating the deficiency of the calorific value of the fixing belt. The magnetic characteristic of the magnetic shunt alloy layer varies according to the temperature. The magnetic shunt alloy layer is transformed from a ferromagnetic body into a paramagnetic body at a curie point. The magnetic shunt alloy layer generates heat itself. The magnetic shunt alloy layer loses its magnetism and does not generate heat any more at the curie point. The calorific value of the fixing belt may be excessively increased due to the heat generated by the magnetic shunt alloy layer itself, which may lead to a problem that the heating efficiency of the fixing belt cannot be improved.