The invention discloses a fully-automatic nut tapping machine. The fully-automatic nut tapping machine comprises a fixed machine head, a feeding device, a limiting module and a movable machine head, wherein a feeding hole is formed in the fixed machine head; the feeding device is arranged at the feeding end of the fixed machine head; clamping blocks, aided tools, the limiting module and the movable machine head are sequentially arranged at the discharge end of the fixed machine head; the clamping blocks are mounted on the fixed machine head and uniformly distributed on the periphery of the feeding hole; a plurality of tool seats are mounted on the fixed machine head, and the aided tools are mounted on the tool seats; a mounting hole is formed in the limiting module, an auxiliary column is mounted in the mounting hole, and a limiting hole is formed in the auxiliary column; a drill bit and a tapping bit are arranged on the movable machine head and each of the drill bit and the tapping bit is directly connected with a power device. According to the fully-automatic nut tapping machine, power devices are directly connected with the drill bit and the tapping bit, so that the equipment stability and the machining precision are improved.