Abstract: A pannier includes: a casing body; a lid; an attaching-detaching holder which removably attaches the casing body to the vehicle; an opening-closing holder which attaches the lid in an openable and closeable manner; a cylinder which serves to lock both of the attaching-detaching holder and the opening-closing holder; and first and second movable holders which are movable when the cylinder is unlocked. At a lock position of the cylinder, the first and second movable holders are retained at a position where the casing body is unremovable and the lid is unopenable. At a pannier detaching position off the cylinder, the second movable holder is movable to an attachable-detachable position where the movable holder allows the casing body to be detached. At a pannier opening position of the cylinder, the first movable holder is movable to an openable position where the movable holder allows the lid to be opened.