The invention relates to the field of welding equipment, in particular to a single-shaft gantry type automatic welder. The position of a welding gun can be adjusted according to different welding positions, and the single-shaft gantry type automatic welder is wide in application range and comprises a gantry support. The single-shaft gantry type automatic welder is characterized in that a first bearing block is mounted at the upper end of the gantry support through a first rotating shaft, a swing rod fixedly sleeves the first bearing block, the lower end of the swing rod is connected with a horizontal guide rail, a horizontal sliding seat is arranged at the lower end of the horizontal guide rail, a vertical fixing seat is mounted on the horizontal sliding seat, a vertical lead screw is mounted on the vertical fixing seat and connected with a vertical driving motor, a vertical slider is mounted on the vertical lead screw through a vertical lead screw nut, and a welding gun is mounted on the vertical slider.