In a V-belt continuously variable transmission (CVT), a sheave drive mechanism includes a movable tube coupled to a movable sheave half of a primary sheave so as to be rotatable with respect thereto and axially movable together therewith, a fixed tube disposed internally of and coaxially with the movable tube, and a ball screw mechanism provided between the fixed tube and the movable tube. The sheave drive mechanism further includes an outer peripheral wall arranged to cover the area from a fixed end of the fixed tube to the outer periphery of the movable tube, an oil seal provided between the movable tube and the outer peripheral wall to seal an internal space for enclosing the working surface of the ball screw mechanism, and a communication path for communication between the internal space and the outside of the outer peripheral wall. The V-belt (CVT) has a smooth feed operation of the ball screw mechanism in the sheave drive mechanism and has a high durability attained by waterproofing.