An image forming apparatus includes an image bearing member; developing devices, each of which includes a developer carrying member, having an electrode member, for carrying a developer, and a developer feeding member, having a core metal and a surface foam layer, for supplying the developer to the developer carrying member; a supporting member, supporting the developing devices, for sequentially rotating the developing devices to a developing position; and a controller for executing an operation for reducing non-uniform distributions of the developers in the developing devices on the basis of electrostatic capacities between the electrode members and the core metals, respectively.