Abstract: A concave groove 3 formed in a male spline fitting portion 1a of an inner shaft 1 is filled with a synthetic resin via filling holes 4 formed in a female spline fitting portion 2a of an outer shaft 2. Resinous slide portions 5 are formed on the fitting portions 1a, 2a of these two shafts 1, 2. A resinous ring 6 is attached to an inner peripheral surface of a front side end of the female spline fitting portion 2a of the outer shaft 2, whereby even if the front side end of the outer shaft 2 comes off the male spline fitting portion 1a of the inner shaft 1, the front side end of the outer shaft 2, because of the resinous ring 6 sliding on an outer peripheral surface of a small-diameter portion 1b of the inner shaft 1, is capable of smoothly moving towards a front side of a vehicle.