A developer container has a main part accommodating a developer therein and is detachably attached to a main part of an image forming apparatus. The developer container comprises an outlet provided at a side of the developer container to discharge the developer from the developer container. An input unit is provided adjacent to the outlet and has a small-diameter portion an inside diameter of which is smaller than a diameter of the container main part wherein, when the developer container is attached to the image forming apparatus, the input unit is engaged with a drive motor of the image forming apparatus to receive a rotating force of the drive motor. A developer guiding unit causes the developer inside the developer container to be moved to the outlet beyond the small-diameter portion of the input unit by rotation of the developer container.