To prevent a power roller from being radially shifted so as to improve the durability of each constituent member by superposing a plurality of contact ellipses related to a thrust ball bearing, and thrust load support parts of a thrust bearing over the axial direction of the power roller and an outer ring.

A plurality of contact ellipses 41, 41 related to a thrust ball bearing 26, and support parts of a plurality of needles 33, 33 that are load support parts of a thrust needle bearing 27 are superposed over the axial direction of a power roller 8 and an outer ring 30 so as to reduce bending stress applied to the outer ring 30 on the basis of thrust load applied to the outer ring 20, constituting the thrust ball bearing 26, from a plurality of balls 29, 29 constituting the thrust ball bearing 26. As a result, the power roller 8 is prevented from being radially shifted so as to improve the durability of each constituent member and moreover to improve the durability of the outer ring 30 constituting the thrust ball bearing 26.