PURPOSE: To improve the power transmission efficiency of a V-belt transmission, and extend the lifetime of a V-belt.

CONSTITUTION: A driving side gear 21 and a driven side gear 22 are rotatably supported by movable pulleys 15, 18 of a driving pulley 11 and a driven pulley 12 respectively. The gears 21, 22 are engaged with an operating gear 23. Cam grooves 21b, 21b for making engaging contact with rollers 28, 30 on the transmission main frame side to convert the rotating operation in the axial operation are provided in each gear 21, 22. Since a V-belt 13 is not pinched by the spring force of the driven pulley 12, the minimum necessary friction force is applied to the V-belt 13 for power transmission.