PURPOSE: To enhance the appearance, decrease the number of constituent parts, and perform the assembly works quickly by covering internal mechanisms, etc., with a shield member so that they are not exposed from a gap produced between a seat cushion and the finisher upper part when it is elevated by a vertical regulating mechanism.

CONSTITUTION: The top 21a of a shield member 21 is secured to the side of a seat cushion 12, and a sack-shaped part 21b is formed at the bottom of the shield member 21. A crank-shaped wire 23 is inserted in and detained with this sack-shaped part 21b, and a bent part 23a is formed at each end of the wire 23. The bent parts 23a are rotatably detained with a through hole 25a in a detention part 25 furnished inside of a finisher 11. The shield member 21 is energized as retrtacted downward at normal times.