PURPOSE: To provide a lighter, stronger shaft member which is formed of low- cost material and used for the connection of an industrial machine such as a transportation machine, an internal combustion engine, a processing machine, a working machine, etc.

CONSTITUTION: Cylindrical shaft materials 10 are provided in a sectional H or U shape and firmly welded at mutual opening end faces 12 to form a hollow shaft mainframe 15. Formed in the hollow portion 11 of the hollow shaft mainframe 15 is at least two reinforcing walls 14, which intersect the hollow shaft mainframe 15 at a right angle to the axial direction, at a hollow space 18.