PURPOSE: To improve the thermal efficiency and reduce the wait time considerably, by covering the outside circumference of a fixing roller with an electrically conductive and thermally conductive thin layer and forming an AC magnetic field in the roller and subjecting the conductive thin layer on the outside circumference to induction heating.

CONSTITUTION: In respect to a fixing roller 16 to which the toner image faces of a form is pressed, the outside circumference of an electrically insulating and thermally insulating layer 18 is covered with an electrically conductive and highly thermal conductivity thin layer 19, and this layer 19 is covered with a heat resisting and releasing thin layer 20 such as "Teflon ". A closed magnetic circuit is formed across the fixing roller 16 by a permeably core material 21a, and a primery winding 21b is provided in a part of the core material 21a, and an AC is supplied to this primary winding by an AC applying means 21c to subject the conductive thin layer 19 near the surface of the fixing roller 16 to induction heating. Since the thin layer 19 has a small heat capacity because of the thin layer, the temperature rises in a short time; and the surface temperature distribution becomes uniform because the thin layer 19 is a good heat conductor.