PURPOSE: To make the driving noise of a toner tank small, to decrease vibration and further to move the tank at a high variable speed by setting a DC motor as a driving source.

CONSTITUTION: A command pulse signal is generated by a command pulse signal generation means (pulse generator) 7 and converted into a DC voltage by a conversion means (digital/analog converter) 3d, and the DC motor 8 is driven by the DC voltage so that the toner tank 11 is driven to be carried to a developing area by a driving means 9 where the motor 8 is set as the driving source. At such a time, a response pulse signal in accordance with the rotation of the motor 8 is generated by the response pulse signal generation means 7. Then, an error signal generation means 3 detects an error between the command pulse signal and the response pulse signal and generates an error signal, and a control means controls the DC voltage converted by the means 3d based on the error signal.