PURPOSE: To smoothly transmit and speed-shift ultra-high speed power by providing a planetary roller mechanism having a special roller configuration and a hydraulic pressurizing mechanism so as to produce a high local pressure at the contact point of each roller so as to generate a high traction for power transmission.

CONSTITUTION: At least three planetary rollers 3 have each convex curved surfaces at both shoulder parts of its outer peripheral surface which are made into press-contact with two left and right rings 4, 4' having inner peripheral surfaces of cone-like shapes with equal inclined angles so that the three planetary rollers 3 are made into press-contact with the outer periphery of a sun roller 2 under the presence of oil. At least one of the outer contact rings 4, 4' is unrotatable but movable in the axial direction, and is pressed against the planetary roller 3 side by means of ring-like bellows 11. Further, each planetary roller 3 is concentrically split into a planetary shaft 6 side roller part 3a and an outer peripheral side ring part 3b with a gap 16 therebetween, and further, the sun roller 2 is coupled to a high speed shaft 5 while the planetary rollers 3 are coupled to a low speed shaft 8 by way of a carrier 7.