A receiving member is configured to receive a driving force from outside, is mounted on a first side wall on an opposite side from a developer accommodating portion, and is rotatable around a first axis line parallel to the longitudinal direction. A rotating member is rotatably provided between the first and second side walls, and configured to be rotated by the driving force received by the receiving member. A detection body is mounted on the second side wall on an opposite side from the developer accommodating portion and includes a detected part which is detected by a detecting unit. The detection body advances outwards in the longitudinal direction with respect to the second side wall and retracts inwards in the longitudinal direction with respect to the second side wall by the driving force received by the receiving member.