The invention discloses a full-automatic corner welding device. The full-automatic corner welding device is used for welding busbars during production of photovoltaic modules. The full-automatic corner welding device is provided with a positioning disc and a rotary circular disc which is coaxially arranged on the outer side of the positioning disc, wherein the positioning disc is provided with a traction feeding unit, a welding unit and a discharging unit which are orthogonally and axially distributed, and a long-edge weld strip loading work station, a short-edge weld strip loading work station, a welding work station and a discharging work station are formed; and corner welding carrying stands provided with L-shaped grooves are fixedly arranged in circular-ring quartering positions of the rotary circular disc, and the corner welding carrying stands are located on the four work stations periodically and alternately along with rotation of the rotary circular disc to conduct full-automatic corner welding. The full-automatic corner welding device is simple in structure, convenient to operate and high in automation degree; and the problems that the work efficiency of right-angled busbar welding is low, and right-angle precision is hard to guarantee are perfectly solved, and the effect of the full-automatic corner welding device on corner welding work of the busbars of the photovoltaic modules is irreplaceable.