Automatic bolt tightening device and workpiece machining device

The utility model discloses an automatic bolt tightening device which is arranged in a workpiece machining body and comprises a sleeve switching mechanism and an automatic constant twisting mechanism. A first adjusting end of the automatic constant-torque mechanism is connected with the workpiece machining main body, so that a second adjusting end of the automatic constant-torque mechanism is driven by the workpiece machining main body to move to a first designated position relative to the switching end of the sleeve switching mechanism; a second adjusting end of the automatic constant torque mechanism automatically adjusts a second specified position relative to the switching end of the sleeve switching mechanism; a part of the positioning end of the sleeve switching mechanism is arranged on the ground, the positioning end of the sleeve switching mechanism can conduct positioning adjustment relative to a bolt on a workpiece, the switching end of the sleeve switching mechanism is arranged relative to a bolt o