To reduce press-in failures when mutually joining two rotating shafts constituting a steering shaft to be rotated coaxially with a steering wheel.

A cylindrical joint portion 11 having an inner diameter d coaxial with the rotating shaft is formed at the lower end of the rotating shaft 1 on the upper side, a cylindrical joint portion 21 coaxial with the rotating shaft is formed at the upper end of the rotating shaft 2 on the lower side, and an engagement portion 22 consisting of a plurality of protruded strips to be bitten into the inner face of the joint portion 11 in engaging therewith is formed on the outer face of the joint portion 21. The engagement portion 22 is harder than the joint portion 11. When both joint portions 11, 21 are joined to each other, the engagement portion 22 is bitten into the inner face of the joint portion 11 in engaging therewith, thus reducing press-in failures.