PURPOSE: To prevent a difference in driving speed from being generated between driving bodies even in a transient state, by providing one of driving bodies the load on which is lower than the load on the other driving body with a means for exerting a load difference, and exerting a load on the driving body receiving the lower load for a predetermined period of time when the driving bodies are started and when the driving bodies are stopped.

CONSTITUTION: In a driver for a printer comprising four photosensitive drums 3AW3D and a feeding belt 1 for feeding a transfer paper 14 in contact with the drums, the load on a motor provided with a belt-driving roller M1 is lower then the load on a motor for driving the drums 3AW3D. A torque brake 20 is provided for a roller shaft 19 between the belt-driving motor 18 and the belt-driving motor M1, and the torque brake 20 is so operated that equal loads are exerted on both the driving body for the drums and the driving body for the belt. The torque brake 20 is energized for a predetermined period of time in a transient state when the belt-driving motor 18 and the drum-driving motor are started and when the motors are stopped, whereby rise and fall conditions with the same velocity change can be maintained between the feeding belt 1 and the drums 3AW3D.