The invention discloses a nut tightening device, and relates to the technical field of hardware machining application. The nut tightening device comprises a feeding mechanism, a screwing mechanism anda discharging mechanism; and the feeding mechanism is used for transporting workpieces with nuts being pre-mounted at the tops to the discharging mechanism, the screwing mechanism is used for screwing the pre-mounted nuts on the workpieces, and the discharging mechanism is used for transporting the screwed workpieces out. The nut tightening device has the beneficial effects that a disc is utilized to rotatably transport the workpieces needing to be machined, the machining efficiency of the workpieces is effectively improved, when the workpieces are rotatably transported to the position over afunnel, the workpieces fall into the funnel through a through hole in a lantern ring and then fall into a storage box through the funnel to be collected and preserved, and thus storage and preservation of the workpieces are facilitated; and by arranging a lead screw, a user can rotate a rotating handle and rotate the lead screw to finely adjust the position of a mounting plate in the up-down direction, it is ensured that the workpieces with the different heights can be clamped and fixed by a clamping head on the mounting plate, thus the nut tightening device can be applied to machining of theworkpieces with the different specifications, and the applicability of the nut tightening device is improved.