A fixing device includes an excitation coil, a rotatable heater, and a support shaft. The excitation coil includes a turning end and an extended portion continuous with the turning end. The heater includes a heat generation layer and a thermosensitive magnetic body composed to switch between magnetized and demagnetized states at a Curie temperature to selectively create localized heating areas in the heat generation layer. The support shaft is made of a nonmagnetic material having a lower electrical resistivity than the thermosensitive magnetic body and supports opposed ends of the heater axially along the heater. The support shaft includes a body portion having a largest outer diameter of the support shaft and an end positioned outside the turning end of the excitation coil, and support portions having a smallest outer diameter of the support shaft and supporting the heater.