An image forming apparatus, comprising: an image forming apparatus body; a first driving mechanism located in the image forming apparatus body; a first drive unit including an input unit to which a rotary drive power is transmitted from the first driving mechanism; an image carrier that carries an electrostatic latent image; a developing device removably attachable to the image forming apparatus body, the developing device forming a toner image on the surface of the image carrier, the toner image corresponding to the electrostatic latent image; and a biasing member biasing the developing device toward the image carrier side, wherein the developing device includes a developing roller supplying toner onto the image carrier, and a developing unit housing and supporting the developing roller, the first drive unit is located at one end portion in an axial direction of the developing roller, the developing unit is configured to swing to come close to the image carrier by the biasing member biasing the developing unit, and the developing unit is swingable with respect to the first drive unit, characterized by the image forming apparatus further comprising a gear; wherein, the first drive unit receives the rotary drive power transmitted from the first driving mechanism via the gear, and the first drive unit is secured to the image forming apparatus body, the image forming apparatus further comprising a toner replenishment container housing the toner to be replenished to the developing device; a toner replenishment screw located in the toner replenishment container; a second driving mechanism located in the image forming apparatus body; a second drive unit transmitting a rotary drive power from the second driving mechanism to the developing roller; and a coupling joint, wherein the first drive unit transmits the rotary drive power to the toner replenishment screw, the second drive unit is located at another end portion in the axial direction of the developing roller, and the second drive unit receives the rotary drive power transmitted from the second driving mechanism via the coupling joint, wherein a center shaft for swinging of the developing unit with respect to the first drive unit is located coaxially with a center shaft for swinging of the developing unit with respect to the image forming apparatus body. an image forming apparatus body; a first driving mechanism located in the image forming apparatus body; a first drive unit including an input unit to which a rotary drive power is transmitted from the first driving mechanism; an image carrier that carries an electrostatic latent image; a developing device removably attachable to the image forming apparatus body, the developing device forming a toner image on the surface of the image carrier, the toner image corresponding to the electrostatic latent image; and a biasing member biasing the developing device toward the image carrier side, wherein the developing device includes a developing roller supplying toner onto the image carrier, and a developing unit housing and supporting the developing roller, the first drive unit is located at one end portion in an axial direction of the developing roller, the developing unit is configured to swing to come close to the image carrier by the biasing member biasing the developing unit, and the developing unit is swingable with respect to the first drive unit, characterized by the image forming apparatus further comprising a gear; wherein, the first drive unit receives the rotary drive power transmitted from the first driving mechanism via the gear, and the first drive unit is secured to the image forming apparatus body, the image forming apparatus further comprising a toner replenishment container housing the toner to be replenished to the developing device; a toner replenishment screw located in the toner replenishment container; a second driving mechanism located in the image forming apparatus body; a second drive unit transmitting a rotary drive power from the second driving mechanism to the developing roller; and a coupling joint, wherein the first drive unit transmits the rotary drive power to the toner replenishment screw, the second drive unit is located at another end portion in the axial direction of the developing roller, and the second drive unit receives the rotary drive power transmitted from the second driving mechanism via the coupling joint, wherein a center shaft for swinging of the developing unit with respect to the first drive unit is located coaxially with a center shaft for swinging of the developing unit with respect to the image forming apparatus body.