A supporting unit for supporting a rotatable member to feed a developer includes a frame including a first surface extending in a direction crossing an axis of the rotatable member and a second surface extending in a direction crossing the first surface, and a fixed member. The fixed member includes (i) a first opposing surface opposing and contacting the first surface, (ii) a second opposing surface opposing the second surface, and (iii) a first front side surface opposite from the second opposing surface. The second opposing surface is welded to the second surface by ultrasonic spot welding such that a first recess is formed on the first front side surface.