A conventional cord having bulges is provided with an elastic rubber core and exhibits a difference in elongation or contraction between the rubber part corresponding to the end of each bulge and the rubber part corresponding to the center thereof. Namely, a part which undergoes severe elongation and contraction and a part which does not undergo elongation or contraction coexist in the elastic core. Therefore, a high strain is accumulated in the boundary region between both parts, so that the core results in rupture when the strain reaches a limit. Such a conventional cord is disadvantageous in that a relatively weak material such as rubber is unavoidably subjected to operation causative of strain accumulation. The present invention is a cord provided with a tubular cord body that is made of a stretchable material and that has bulges which are repeatedly arranged with spaces thereamong and the diameters of which change in dependence on the axial tension applied to the cord body.
