PURPOSE: To achieve both a high print speed and a high print quality, by driving a mounted wheel by a predetermined angle through a predetermined angle driving means prior to the start of printing operation and setting the driving conditions of a rotary control means on the basis of an output from a comparison means.

CONSTITUTION: An inertia moment is splitted into 1W3 groups and control conditions IWIII are set for them. Furthermore, control conditions of a means 41 for driving a wheel by predetermined angle, or control conditions S having an intermediate inertia moment for a randomly selected angle, and an operating time are set. When power is turned on or a wheel is replaced, the wheel is rotated by 180° from the home position on the basis of the control conditions S. Then the actual operating time is detected and compared with a preset operating time. On the basis of the comparison results, it is modified and set automatically to a drive current level satisfying the optimal control conditions being preset in a selection motor drive current control means 45.