A fuser includes: a heat generating section including a heat generating layer and configured to rotationally travel; an induction-current generating section provided around the exterior of the heat generating section and including an exciting coil and an external ferrite core that covers the outer circumference of the exciting coil; an opposing section set in contact with the outer circumferential surface of the heat generating section; and an internal ferrite core arranged inside of the heat generating section in a position opposed to the exciting coil, a first center angle connecting both edges of the internal ferrite core and a rotation center of the heat generating section being larger than a second center angle connecting both edges of the external ferrite core and the rotation center of the heat generating section.