A four-row cylindrical roller bearing is incorporated into between the inner peripheral surface of a housing and the outer peripheral surface of a backup roller. A sensor unit 7 is held in a portion of a collar disposed in the axial-direction end portion of the four-row cylindrical roller bearing. The sensor unit comprises a detect part for detecting temperatures and vibrations and a transmitter device for transmitting signals, which are obtained after output signals taken out from the detect part are processed, as radio signals. On a portion of a hold cover which is a separate member from the collar, there is disposed a receive antenna which is part of a receiver apparatus for receiving the radio signals transmitted by the transmitter device.