Abstract: A support part attached to a developer container used in an electrophotographic image forming apparatus includes a support portion for supporting one end of an agitating member for agitating developer contained in the developer container, a fitting portion fitted into a through hole formed in a frame of the developer container, a detent portion for preventing the support part from disengaging from the through hole, a seal member contacting portion for contacting a seal member for preventing developer from leaking from between the frame and the support part, and a driving force receiving portion for receiving a driving force for rotating the support part. In a direction intersecting with an axis of the support part, the detent portion is positioned inwardly of an outer peripheral surface of the seal member contacting portion.