PURPOSE: To reduce the extent of noise by using plural pieces of planetary rollers pivoted aslant to a fange outer circumference of a power transmission shaft, a tube concentrically locked to a control gear externally fitted in these rollers and a sun roller detachable to a planetary roller inner circumference in this tube.

CONSTITUTION: Rotation of an input shaft 1 at an HS mode rotates a fixed hydraulic unit 17 through discharge oil in a quantity conformed a position of a stroke control means 19 from a variable hydraulic unit 16, and an output shaft 15 rotates via a control gear 11, a clutch means 38 and a turning shaft 28. Likewise, rotation of the input shaft 1 at an HM mode rotates a tube 26 of the control gear 11, a power transmission shaft 8 and a flange 9 from the fixed hydraulic unit 17, and since each outer circumference of a guide ring 27 of the tube 26 and a sun roller 29 come into contact with two planetary rollers of plural fulcrum shafts 24 installed in this outer circumference of the flange 9 projectingly, rotational speed in the sun roller 9 canes to a resultant speed of the flange 9 and the tube 26, thus it is transmitted to the output shaft 15 via the turning shaft 28. In this constitution, the extent of noise is reduced, while one clutch is omittable, thereby simplifying the structure.