A container seal arranged on a receiving opening of a powder container including a container shutter that moves from a closing position for closing the receiving opening to an opening position for opening the receiving opening due to a contact with a conveying nozzle of an image forming apparatus, wherein the container seal is formed with a penetrated portion through which a nozzle shutter arranged on an outer side of the conveying nozzle penetrate in a first moving direction in which the container shutter moves from the closing position to the opening position; an inner circumference of the penetrated portion serves as a sliding-contact surface that rotates relative to an outer circumference of the nozzle shutter while coming in sliding-contact with the outer circumference of the nozzle shutter at the opening position; and the sliding-contact surface is formed such that a frictional force between the sliding-contact surface and the nozzle shutter, of the upstream side in the first moving direction becomes lower than a frictional force between the sliding-contact surface and the nozzle shutter, of the downstream side.