To surely and stably energize a transfer roller and to transfer a toner image from photoreceptor to paper with good image quality by providing an energizing auxiliary means presscontacting with the shaft end part of the transfer roller and applying high voltage from a high voltage power source on the transfer roller.

At the time of printing, the transfer roller 31 is energized from the high voltage power source 36 through a sheet metal 37, a spring member 35 and a bearing member 34, and energized through the sheet metal 37, the spring member 35 and the energizing auxiliary member 40. Even when toner enters a gap between the hole 34a of the bearing member 34 and the shaft end 32a of the roller 31 and electric connection between the member 34 and the roller 31 becomes unstable, faulty energizing is prevented because the roller 31 is energized through the member 40. Therefore, the visible toner image on the peripheral surface of the photoreceptor 21 is transferred on the surface of the paper with good image quality. Then, whatever mechanism is allowed when it is the mechanism energizing the roller 31 by the means 40 without through the member 34.