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 formed on the back end surface of the toner container ; a positioning pin provided in the toner-container receiver so as to face the positioning hole ; a retracting assembly 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 into the positioning hole through the retracting assembly 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 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 formed on the back end surface of the toner container ; a positioning pin provided in the toner-container receiver so as to face the positioning hole ; a retracting assembly 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 into the positioning hole through the retracting assembly 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 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. <EOS>