An image forming apparatus includes a plurality of developing devices, each of which includes a developer carrying member for carrying a developer to develop an electrostatic image formed on an image bearing member with a developer, and a developer regulating member for regulating the developer carried on the developer carrying member; a common voltage applying device for applying voltages to the developer regulating members, wherein the voltages are applied to the developer carrying members are variable independently from each other, and when at least one of the voltages varies, the voltage applied by the voltage applying device is capable of being changed.