A ring-like lubricant supply device 6 is fitted into a recess 4 of a nut member 2. The lubricant supply device 6 contains a lubricant and is formed in an outer peripheral surface with notches 7. Tubular members 8 each having an outer diameter larger than the diameter of the notch 7 are inserted into the notches, pushing and widening the notches 7 in a circumferential direction. One end of the tubular member 8 is fitted into a recess 9b of a retaining ring 9 and the retaining ring 9 is fixed to a nut member 2.