A developer case that contains developer and supplies the developer to another device in a specified replenishing position includes a main body and a rotating unit. The main body includes a bottom wall, a top wall, and first and second side walls. The rotating unit includes a rotation shaft, a transportation member, and a drive input member. The first and second side walls respectively have first and second linear inner surfaces. When the developer case is in the replenishing position, when a line perpendicular to a horizontal line that passes through an axis of the rotation shaft is defined as a reference line, a first angle θ1 formed between the reference line and the first linear inner surface is less than a second angle θ2 formed between the reference line and the second linear inner surface.