PURPOSE: To execute speed change operation from the outside by a method wherein a variable speed pulley mechanism and a differential gear mechanism are respectively surrounded with a closed case, an operation shaft is supported in an insertion state at a case on the variable speed pulley mechanism side, a crank arm is attached to the operation shaft, and the tip part thereof is coupled to the drive part of the variable speed pulley mechanism.

CONSTITUTION: An operation shaft 73 extending in a direction crossing an input shaft 8 (an intermediate shaft 14) approximately at right angles is rotatably supported in an insertion through-hole 72, formed through the side wall 3b of a second division case 3 being a pulley case 6, by means of a bearing 74. One end of the operation shaft 73 is extended to the outside of a transmission case and an operation lever is rotatably and integrally arranged. The other end of the operation shaft 73 is positioned in the pulley case 6 of a transmission case and the base end of a crank arm 75 is rotatably and integrally fixed. The operation shaft 73 is operated by an operation lever, the pulley ratio of a variable speed pulley is changed, the pinion carrier (the output part) of a planetary gear mechanism is switched into a forward, a neutral, and a reverse state to an input shaft 8.