To make the surface temperature of a roller uniform and also the heat distribution freely controlled when two or more induction coils are excited by a single phase power supply of an induction heating mechanism.

A plurality of the induction coils is arranged in parallel along with an axial center of the roller. The induction coils are divided into a central group located in a central part in alignment with an axial center of a roller, and an end group located in both sides of the central group. The induction coils belonging to each group are separately connected respectively, to a common single-phase power supply collectively, through a voltage regulator. Each temperature detector, which detects the surrounding wall temperature of the roller, which faces the induction coil belonging to the each group, is installed in the surrounding wall of the roller. The voltage regulator is controlled so that the surrounding wall temperature of the roller may become to a predetermined distribution state according to the detected surrounding wall temperature of the roller detected by each the temperature detector.