An annular support ring 32 is fitted onto the outer periphery of each trunnion 22. This support ring 32 and the roller 34 are unitized via a plurality of needle rollers 36 to constitute a roller assembly capable of relative rotations therebetween. In longitudinal section, each trunnion 22 has an outer periphery of straight shape, parallel to the axis of the trunnion 22. In cross section, the trunnion 22 has a generally ellipse shape with the major axis orthogonal to the axis of the joint. The inner periphery of each support ring 32 is arcuate and convex in section. This combines with the general elliptic cross sections of the trunnions 22 and the provision of predetermined clearances between the trunnions 22 and the support rings 32, to allow the support rings 32 to move along the axial directions of the trunnions 22 as well as make tilting movements with respect to the trunnions 22.