A developer unit for an image forming apparatus is provided. The developer unit includes a developer device with a developer agent carrier and a developer agent supplier, and a developer agent container, which contains the developer agent and is arranged in a lower position with respect to the developer device. The developer agent container is formed to have a fitting wall, which is curved inward at a position to be adjacent to the developer device. The fitting wall is formed to have a feeding opening and a collecting opening. The developer unit is further provided with a first conveyer, which is rotated about a rotation axis to sweep an inner surface of the developer agent container and convey the developer agent toward the feeding opening, and a second conveyer, which is arranged along the developer agent supplier and conveys the developer agent toward the collecting opening.