A device for fusing a predetermined toner image on a paper and which electrically insulates a heating body of a fusing unit from a power supply unit by heating the heating body using an induced current generated by a transformer. The fusing device includes an insulation unit for generating an induced current in response to an alternating current, a heating body heated by the generated induced current, a toner fusing unit which fuses the toner image on the paper using the heat received from the heating body, and a tube-expansion adhesion portion closely adhering the heating body to the toner fusing unit using a predetermined tube-expansion pressure.