Abstract: There is provided a frame having closed cross-sections capable of preventing a welded joint of the frame from being turned in a wide open state, or being broken when an external force is applied to the frame at the time of vehicle collision, and so forth, and the frame is collapsed. The frame having closed cross-sections is provided with a body cylindrical in shape, wherein first side parts of a first frame member, in pairs, are welded to second side parts of a second frame member, in pairs, respectively, thereby forming a welded joint on both sides of the body, and respective end faces of each of the reinforcing plates, in the widthwise direction of the body, are butted against respective inner side faces of the side parts of the body, corresponding thereto.