A toner-container support unit, comprising: a toner container housing toner; a container mount including an internal space to accommodate the toner container; a toner-container receiver which is provided on an internal end side of the internal space of the container mount, fixing and supporting a back end surface of the toner container inserted into the container mount; a positioning hole (201, 202) formed on the back end surface of the toner container; a positioning pin (951, 952) provided in the toner-container receiver so as to face the positioning hole (201, 202); a retracting assembly (68, 97) retracting a back end portion of the toner container to the toner-container receiver side when inserting the toner container into the container mount, a position of the toner container being adjusted by fitting the positioning pin (951, 952) into the positioning hole (201, 202) through the retracting assembly (68, 97) retracting the back end portion of the toner container; and an inclination stopper which prevents the inclination of the toner container when the back end portion of the toner container is retracted by the retracting assembly toward the toner-container receiver, characterized in that the retracting assembly (68, 97) includes a fixed protrusion which is disposed on each of the side wall sections of the toner container, and a movable protrusion which is disposed on each of the inner sides of the container mount and has a biasing force toward the outside, wherein when inserting the toner container into the container mount, the movable protrusion contacts the fixed protrusion and moves over the fixed protrusion while being pushed by the fixed protrusion, then the movable protrusion goes back by the biasing force so that the retracting assembly retracts the back end portion of the toner container to the toner-container receiver side. a toner container housing toner; a container mount including an internal space to accommodate the toner container; a toner-container receiver which is provided on an internal end side of the internal space of the container mount, fixing and supporting a back end surface of the toner container inserted into the container mount; a positioning hole (201, 202) formed on the back end surface of the toner container; a positioning pin (951, 952) provided in the toner-container receiver so as to face the positioning hole (201, 202); a retracting assembly (68, 97) retracting a back end portion of the toner container to the toner-container receiver side when inserting the toner container into the container mount, a position of the toner container being adjusted by fitting the positioning pin (951, 952) into the positioning hole (201, 202) through the retracting assembly (68, 97) retracting the back end portion of the toner container; and an inclination stopper which prevents the inclination of the toner container when the back end portion of the toner container is retracted by the retracting assembly toward the toner-container receiver, characterized in that the retracting assembly (68, 97) includes a fixed protrusion which is disposed on each of the side wall sections of the toner container, and a movable protrusion which is disposed on each of the inner sides of the container mount and has a biasing force toward the outside, wherein when inserting the toner container into the container mount, the movable protrusion contacts the fixed protrusion and moves over the fixed protrusion while being pushed by the fixed protrusion, then the movable protrusion goes back by the biasing force so that the retracting assembly retracts the back end portion of the toner container to the toner-container receiver side.