A developer storing container includes a developer storing portion having a developer outlet opening at a substantially longitudinal center portion, and an agitation member rotatable about a rotation axis to thereby agitate and eject the developer via the developer outlet opening. The agitation member includes a mounting portion with a mounting surface along the rotation axis, and an elongated flexible member having first and second ends. The flexible member is mounted to the mounting portion at the first end so that the second end defines a sliding end portion at which the flexible member slides in a sliding direction. Both longitudinal end portions of the sliding end portion of the flexible member slide along the inner surface of the developer storing container, ahead of a substantially longitudinal center portion of the sliding end portion in the sliding direction, and are inclined with respect to a direction perpendicular to the sliding direction.