PURPOSE: To easily correct the picture forming mode of a copying device when a setting means automatically sets the picture forming mode in accordance with the realized combined variable power rate of the minimum number of times calculated by a magnification calculating means, by returning the mode to the preceding picture forming mode one after another.

CONSTITUTION: If a mode setting key 43 is depressed when an out of-set-range variable power mode is set by depressing another mode setting key 44 and during a fixed waiting time, a flow is started and '1' is added to a repeat counter, and then, the picture forming mode of one stage before is restored. In case of the final picture forming mode during plural times of picture forming modes, the maximum or minimum variable power rate is set as the variable power rate. Therefore, a copying mode can efficiently be set and corrected.