A first slip joint and a second slip joint are respectively arranged on a member mounted within an upper part of a car and a member mounted within a lower part of a car, a retractor is mounted on a side wall inside the car body (upon, for example, a center pillar) between the first and second slip joints, and a shoulder belt and a lap belt are respectively conducted from the retractor to a tongue plate through the first slip joint and through the second slip joint. A load which is exerted on a mounting portion of the retractor when the car body is suddenly decelerated can be confined to below approximately 50 Kg.