PURPOSE: To prevent transverse slippage from occurring between a current-supplying brush and an annular electrode and maintain stable current supply to a heating roller, by providing one of a tip surface of the current-supplying brush and the surface of the annular electrode with a recessed part along a peripheral surface, and providing the other with a projecting part to be engaged with the recessed part.

CONSTITUTION: The surface of each of current-supplying rings 28a, 28b is provided with an arcuate recessed part along a circumferential surface, while a tip surface of each of current-supplying brushes 33a, 33b to be brought into sliding contact with on the rings 28a, 28b is provided with an arcuate projecting part to be engaged with the corresponding recessed part. Thus, even when transverse slippage occurs between the rings 28a, 28b and the tip surfaces of the brushes 33a, 33b, sliding contact parts of them can be maintained in an engaged condition. As a result, it is possible to prevent the tip surfaces of the brushes from being deformed through abrasion and to prevent contact resistance from being increased, and stable current supply to a heating roller 21 can be maintained. A large contact area can be secured between the ring and the brush, so that the width of the ring and the brush can be reduced accordingly, and it is possible to maintain a sliding contact condition stable to transverse slippage.