To effectively improve first copying speed while balancing the printing speed of an image forming device with the life of a polygon motor.

A CPU 11 collects information on the frequency in use of the polygon motor in accordance with the day of the week and a time zone and stores the collected information in a flash ROM 15. The information on the frequency in use concerning each time zone is classified and the level of the frequency in use is made to correspond to the time zone. The level of the frequency in use is previously made to correspond to the pre-scanning speed of the polygon motor. The pre-scanning speed made to correspond to the level of the frequency in use corresponding to the present time zone is confirmed at the time of performing operation, and the pre-scanning control is performed at the pre-scanning speed. Thus, the first copying time in the time zone in which the frequency in use is high is automatically shortened. The life of the polygon motor is taken into consideration by calculating the using rate of the polygon motor and making the pre-scanning speed lower as the using rate gets larger.