To improve the operability by a speed-change cable and to reduce the cable by selecting an adequate arrangement structure of the speed-change cable from a transmission case to an operating element of a handle on the front portion of a vehicle body. An arrangement structure of a speed-change cable is such that the speed-change cable is attached at one end to an arm portion of a derailleur and the speed-change cable is guided from the mounting portion through an outer cable mounting hole of a derailleur shaft to a through-hole opening at the upper front portion of a transmission case, and extends from the through-hole outside the case and along the front frame of the vehicle body substantially straight. The extended end is attached to a cable operation mechanism at the handle on the front portion of the vehicle body.