The invention provides a device for tightening up a plurality of threaded members at the same time with proper torque without necessitating the cumbersome procedure of rotating the members one by one through a specified small angle at a time and without unequivalent tightening of the members. The tightening device 1 comprises two rotary shafts 6 each provided at a forward end thereof with a wrench portion 8 fittable to the threaded member 44, motors 3 for individually driving the rotary shafts 6 and a control unit 9 for detecting the tightening torque of each threaded member 44 and controlling the motor 3 based on the detected value to ensure proper tightening. The control unit 9 checks the tightening torque of each threaded member 44 as to whether the torque is within a predetermined range and whether the difference in tightening torque between the threaded members 44 is within a predetermined range.
