Abstract: It is an object of the present invention to provide a mandrel bar cleaning facility capable of effectively suppressing carburization generated on the inner surface of a pipe or tube while the pipe or tube is elongated and rolled without hindering an operation. A mandrel bar cleaning facility of the present invention cleans a mandrel bar B which is pulled out of a mandrel bar conveying line after being used for elongating and rolling a pipe or tube in a mandrel mill. The mandrel bar cleaning facility is provided with conveying devices that convey the mandrel bar B in the axial direction while revolving the mandrel bar B in the peripheral direction, and cleaning devices that are arranged oppositely to the side of the mandrel bar B conveyed by the conveying devices and jet high-pressure water having a water pressure of 0.2 to 150 MPa (preferably, 20 to 150 MPa) toward the outer surface of the mandrel bar B.