The clearance between the outer peripheral surface of an annular portion of a cage and the inner peripheral surface of each of rib portions of outer-ring split pieces is set to be smaller than the clearance between the radial end surface of a projection portion of the cage and the inner peripheral surface of each of body portions of the outer-ring split pieces. When a centrifugal force due to engine rotation acts upon the cage, the inner peripheral surface of each of the rib portions of the outer-ring split pieces touches the outer peripheral surface of the annular portion of the cage before the inner peripheral surface of each of the body portions of the outer-ring split pieces touches the radial end surface of the projection portion of the cage. Thus, the radial displacement of the cage can be prevented in good time.