A screw tightening apparatus has a stand, a support framework attached slidably in the vertical direction to the stand, an arm section extending horizontally from and connected turnably in a horizontal plane to the support framework, a driving unit mounted on the base end of the arm section for turning the arm section, a screw tightening unit mounted on the leading end of the arm section, and a reaction force absorbing mechanism acted upon tightening a screw. The reaction force absorbing mechanism is provided in the screw tightening unit or the arm section. |