To reduce processes of "spot welding" in a connection structure between one side fitting base plate and the connection bar of the plate.

In the connection structure of the seat and the connection bar in a handle seat unit, at least one engagement notch 25 is formed in the radial direction from the inner peripheral face in a fitting hole 4A formed at the circular vertical wall 22 of one side fitting base plate 1A and the connection bar 3A having a flange 10A engaged with at least one engagement protrusion 30 engaged with the engagement notch 25 and the circular perpendicular wall 22 are inserted. The connection bar 3A is regulated by the internal wall face 32 of the circular wall 7b of one side decoration cap 7A in an integrally fixed relation with the one side fitting base plate 1A.