To inexpensively manufacture a wide variety of screw spindles of a height adjusting device without using a great of costs in a manufacturing facility.

The height adjusting device is comprised by piercing a base piercing part 7 provided on a lower end of the screw spindle 4 having a male screw part 10 and a base external tool fitting part 6 through a through-hole of a base, and mounting the screw spindle 4 capable of slightly swinging in all directions and capable of rotating around an axis to the base. A shaft like material 14 of a head 13b of a bolt 13 is joined by friction welding, and the screw spindle 4, the base external tool fitting part 6, and the base piercing part 7 are respectively composed by the integrated bolt 13 and shaft like material 14, the head 13b of the bolt 13, and the shaft like material 14.