An image forming apparatus includes plural toner image forming devices. Each of which has a rotating photoconductor, a charging device that uniformly charges a surface of the photoconductor, a latent image forming device that forms an electrostatic latent image on the surface of the charged photoconductor, a developing device that develops the electrostatic latent image on the surface of the photoconductor to a toner image, and a developing container that contains toner used by the developing device. A diameter of the photoconductor of at least one toner image forming device is formed larger than a diameter of the photoconductor of the other toner image forming devices. Each developing container of all the toner image forming devices is formed in equal-sized, and a center of rotation of a developing roll of each developing device is arranged in a position upper than a center of rotation of each photoconductor.