A slide member is slidable along a slide rail provided at a vehicle-body side portion. When lock pawls provided at the slide member are engaged with the slide rail, the slide member is locked. The slide member is unlocked by operating an operation cable connected to the lock pawls. The operation cable is fitted to a fitting portion of an attachment bracket connected to the slide rail. A portion from a fixed portion fixed to the fitting portion to a movable portion (one end portion) extends through a region where a non-contact portion is disposed, and does not contact the non-contact portion. The movable portion is connected to the slide member and moved integrally with the slide member.