A V-face of a metal element is prevented from being inclined due to a load from a pulley by increasing the height Hs of an upper non-contact portion of the V-face of the metal element. For example, when the height of the V-face is represented by Hv (mm), and the height of the upper non-contact portion of the V-face is represented by Hs (mm), the height Hv of the V-face and the height Hs of the upper non-contact portion are set so that a relationship −0.5265Hv+2.768≦Hs≦−0.5934Hv+3.524 is established.