Where a magnification (enlargement/reduction of image) has been set through operation keys of an operation panel, a main CPU sends information on read magnification to a scanner CPU of a scanner section. In this case, where the magnification is not set in particular, information of 100% magnification is sent to the scanner CPU. Based on a microstep division number of a step angle corresponding to the received information on read magnification, the scanner CPU controls the driving of a scan motor via a scan motor driver.