PURPOSE: To position a scanner with high accuracy by providing a stopper on a stop position of the scanner, and detaining the scanner to its stopper.

CONSTITUTION: The upper limit of a supply current to a scanner driving motor is controlled to a prescribed value or below in the vicinity of a scanner stop position, a scanner MB1 is detained to stoppers 5a, 5b provided on the scanner stop position and positioned, thereafter, the supply current is stopped. In such a way, when the scanner MB1 is detained to the stoppers 5a, 5b and stopped, the supply current to the driving motor of the scanner MB1 is controlled to a prescribed value or below in the vicinity of the stoppers 5a, 5b. Therefore, the stop position of the scanner MB1 can be positioned exactly, and also, it is prevented that a large burden is applied to a driving circuit of the motor, when the scanner MB1 is detained to the stoppers 5a, 5b.