Propeller shaft

A propeller shaft comprising:

• a first shaft having a yoke at one end;
• a second shaft slidably connected to the other end of the first shaft;
• and
• a surface treated member which is arranged at a connecting portion at which the first shaft and the second shaft are connected to each other, and to which surface treatment for improving slidability of the second shaft with respect to the first shaft is applied,
• wherein:
• the surface treated member is formed of a substrate which is separate from the first shaft and the second shaft and to which the surface treatment is applied, and the surface treated member is arranged at the connecting portion at which the first shaft and the second shaft are connected to each other, after the surface treatment is applied,
• one of the first shaft and the second shaft has first splines, the surface treated member being fixed to the other of the first shaft and the second shaft and having second splines to which the surface treatment is applied;
• the first shaft and the second shaft are connected to each other by slidably engaging the first splines and the second splines with each other,
• the surface treated member and the other of the first shaft and the second shaft are joined at axial end surfaces by friction welding, and
• before friction welding, each of an axial end portion of the surface treated member and an axial end portion of the other of the first shaft and the second shaft, the axial end portions being joined by friction welding, has a bulging portion that has an outer diameter larger than an outer diameter at a time of part completion, wherein the bulging portion is removed together with burr produced by friction welding, during a deburring process that is applied after friction welding.