To prevent a pair of inner ring elements 8 and 8 from inadvertently separating when they are taken off the periphery of an inside member of an axle or the like.

A pair of engaging parts 24 and 24 with a large-diameter part 25 and an engaging groove 26 are formed around the inside peripheral surface of the small-diameter side end of each of the inner ring elements 8 and 8. By engaging each of the extroversion flanges 28 and 28 in each of the engaging grooves 26 and 26 provided on both ends in the axial direction of an engaging ring 27, said pair of inner ring elements 8 and 8 are linked with the ring 27. Under this condition, the inside diameter d27 of the engaging ring 27 is made larger than the inside diameter d8 (d27≥d8) of each body of the inner ring elements 8 and 8 and the level difference L1 of a half of the difference between the inside diameter d27 and d8 is made smaller (L1<L2) than the engaging allowance L2 of a half of the difference between the outside diameter D28 of each of the extroversion flanges 28 and 28 and the inside diameter d25 of each of the large-diameter parts 25 and 25.