A first fit portion and a second fit portion of an inner ring according to the invention have a spring property. Therefore, the first and second fit portions may be flexed radially outward by elasticity thereof and then fitted to a shaft. Thus, the inner ring is tightly fitted to the shaft with a set interference with respect to the shaft. Accordingly, it is easy to fit/remove the inner ring to/from the shaft. Therefore, an outer peripheral face of the shaft is pushed radially inward by elasticity of the first and second fit portions, that is, the inner ring is tightly fitted to the shaft, without reducing the ease of fitting/removing the inner ring to/from the shaft. As a result, it is possible to minimize generation of creep.