A welding device for a non-circular plate, comprising: a chuck for gripping and rotatably supporting a plurality of laminated non-circular plates ; and a welding torch for welding outer peripheral edges of adjacent non-circular plates among the plurality of laminated non-circular plates , the welding device being characterized by further comprising: a stationary shield box ; a movable shield box which is position-adjustable with respect to the welding torch so as to form a shield space (s) surrounding the welding torch with the stationary shield box ; an actuator for enabling position adjustment of the movable shield box with respect to the welding torch ; and a control part for controlling an operation of the actuator based on a rotation angle (θ) of the chuck such that an inner surface of the movable shield box approaches the outer peripheral edges of the adjacent non-circular plates in accordance with the rotation angle (θ), wherein the stationary shield box is disposed so as to surround the welding torch , wherein the movable shield box is disposed on an outer side of the stationary shield box relative to the welding torch , and wherein the stationary shield box and the movable shield box are each provided with a shielding gas supply nozzle . a chuck for gripping and rotatably supporting a plurality of laminated non-circular plates ; and a welding torch for welding outer peripheral edges of adjacent non-circular plates among the plurality of laminated non-circular plates , the welding device being characterized by further comprising: a stationary shield box ; a movable shield box which is position-adjustable with respect to the welding torch so as to form a shield space (s) surrounding the welding torch with the stationary shield box ; an actuator for enabling position adjustment of the movable shield box with respect to the welding torch ; and a control part for controlling an operation of the actuator based on a rotation angle (θ) of the chuck such that an inner surface of the movable shield box approaches the outer peripheral edges of the adjacent non-circular plates in accordance with the rotation angle (θ), wherein the stationary shield box is disposed so as to surround the welding torch , wherein the movable shield box is disposed on an outer side of the stationary shield box relative to the welding torch , and wherein the stationary shield box and the movable shield box are each provided with a shielding gas supply nozzle . a stationary shield box ; a movable shield box which is position-adjustable with respect to the welding torch so as to form a shield space (s) surrounding the welding torch with the stationary shield box ; an actuator for enabling position adjustment of the movable shield box with respect to the welding torch ; and a control part for controlling an operation of the actuator based on a rotation angle (θ) of the chuck such that an inner surface of the movable shield box approaches the outer peripheral edges of the adjacent non-circular plates in accordance with the rotation angle (θ), wherein the stationary shield box is disposed so as to surround the welding torch , wherein the movable shield box is disposed on an outer side of the stationary shield box relative to the welding torch , and wherein the stationary shield box and the movable shield box are each provided with a shielding gas supply nozzle . <EOS>