PURPOSE: To obtain a reducing magnification setting device for a copying machine capable of largely changing reducing magnification in a short time and, on the other hand, capable of preventing a situation that the reducing magnification is hardly set to a desired value because it is suddenly changed.

CONSTITUTION: A microcomputer 25 connected to a reducing magnification setting key such as a magnification up key 21 or a magnification down key 22 constitutes a timer for counting specified set time; a timer control means for starting the timer by setting the set time to a specified initial value when the reducing magnification setting key is depressed, allowing the timer to restart timecounting by resetting the set time shorter every time the timer finishes counting the set time while the reducing magnification setting key is being depressed, and allowing the timer to restart time-counting by holding the set time at a specified lower limited value when the set time reaches the lower limited value; and a means for changing the copying reducing magnification by specified width every time the timer finishes counting the given set time.