PURPOSE: To provide a bolt and nut tightening device of a simple structure by suspending a bolt tightening arm and a rotating and driving nut tightening arm to a stage borne vertically movably on a jack suspended to a mounting plate of an erector device so that they are capable of moving horizontally.

CONSTITUTION: A stage 102 moving vertically along a vertical guide rail 108 by driving of a jack 101 is bore on the jack 101 suspended to a mounting plate of an erector device. Bolt and nut tightening arms 103 and 104 capable of moving in a horizontal direction by a pair of driving jacks are suspended to the stage 102. After that, a bolt A and a nut B fastened to a tightening device 10 side from a supply device are loaded into through-holes of a bolt box 12a of a segment 12, a hydraulic motor 105 is drive to rotate and drive a nut turning section 104a of the arm 104, and the bolt A and nut B are screwed. According to the constitution, loading and controlling can be easily made.