An image forming apparatus including a plurality of process stations vertically arranged each of which includes an image bearing member on which a latent image is to be formed and a developing device for developing the latent image, image bearing member driving devices, for driving the image bearing members, development driving devices, for driving the developing devices, and a transfer material bearing and conveying device for bearing and conveying the transfer material, wherein, while the transfer member is vertically conveyed through transfer nips that are formed by the transfer material bearing and conveying device and the image bearing members of all of the plurality of process stations, images formed by the plurality of pocess stations are sequentially transferred to the transfer material to form an image, and wherein process stations to be used for image forming can be selected, and the image bearing member driving devices and the development driving devices are controlled, so that, during an image forming process, the image bearing members of the process stations that are not used for image forming are driven, while the developing devices thereof are halted.