The present invention has an object to provide an image forming apparatus and method which enables an operator to easily adjust to the desired printing density. A paper feeding roller is driven in timing along with a registration roller. The irradiation of a modulated laser beam is started, a developing high-voltage is changed from "0" V to a predetermined voltage V1, and the voltage is changed to V2 at other timings. By sequentially changing the voltage in this manner, the printing densities from laser modulating data d1 to d10 are adjusted and printing in different densities can be performed.