A device for driving an endless belt of the present invention includes a drive
roller and a roller pair adjoining the drive roller at a side where a photoconductive
element is positioned and contacting the belt. The eccentricity of the drive roller
and that of the roller pair are reduced to reduce the variation of belt speed when
the drive roller is controlled at a preselected angular velocity. Even when the
drum is eccentric, the device stably operates integrally with the belt without
any slip or oscillation.
