An automatic welding machine comprising a link actuation device, the link actuation device including: a proximal end side link hub; a distal end side link hub; and three or more link mechanisms which each couple the distal end side link hub to the proximal end side link hub such that a posture of the distal end side link hub can be changed relative to the proximal end side link hub, characterized in that each of the link mechanisms includes: a proximal side end link member having one end rotatably coupled to the proximal end side link hub; a distal side end link member having one end rotatably coupled to the distal end side link hub; and an intermediate link member having opposite ends rotatably coupled to other ends of the proximal side end link member and the distal side end link member, respectively, each of the link mechanisms has such a shape that a geometric model of the link mechanism wherein the proximal side end link member, distal side end link member and the intermediate link member are each represented by a straight line shows symmetry between a proximal end side portion thereof and a distal end side portion thereof with respect to a center portion of the intermediate link member, and two or more link mechanisms among the three or more link mechanisms are each provided with a posture changing actuator which arbitrarily changes the posture of the distal end side link hub relative to the proximal end side link hub, the link actuation device being disposed on a mount while the proximal end side link hub is on lower side and is directly or indirectly fixed to the mount, a welding torch being mounted to the distal end side link hub which is on upper side, and the link actuation device being provided with both or either one of a one-or-more-axes linear motion actuator (51, 55, 56) which causes the link actuation device to advance and retract relative to the mount, and a one-or-more-axes linear motion actuator which causes a workpiece to advance and retract relative to the mount, the workpiece serving as a target to be subjected to welding work performed by the welding torch, wherein the welding torch is mounted to the distal end side link hub such that a leading end portion, of the welding torch, which performs welding work onto the workpiece faces the proximal end side and protrudes to the proximal end side relative to the proximal end side link hub. a proximal end side link hub; a distal end side link hub; and three or more link mechanisms which each couple the distal end side link hub to the proximal end side link hub such that a posture of the distal end side link hub can be changed relative to the proximal end side link hub, each of the link mechanisms includes: a proximal side end link member having one end rotatably coupled to the proximal end side link hub; a distal side end link member having one end rotatably coupled to the distal end side link hub; and an intermediate link member having opposite ends rotatably coupled to other ends of the proximal side end link member and the distal side end link member, respectively, a proximal side end link member having one end rotatably coupled to the proximal end side link hub; a distal side end link member having one end rotatably coupled to the distal end side link hub; and an intermediate link member having opposite ends rotatably coupled to other ends of the proximal side end link member and the distal side end link member, respectively, each of the link mechanisms has such a shape that a geometric model of the link mechanism wherein the proximal side end link member, distal side end link member and the intermediate link member are each represented by a straight line shows symmetry between a proximal end side portion thereof and a distal end side portion thereof with respect to a center portion of the intermediate link member, and two or more link mechanisms among the three or more link mechanisms are each provided with a posture changing actuator which arbitrarily changes the posture of the distal end side link hub relative to the proximal end side link hub, the link actuation device being disposed on a mount while the proximal end side link hub is on lower side and is directly or indirectly fixed to the mount, a welding torch being mounted to the distal end side link hub which is on upper side, and the link actuation device being provided with both or either one of a one-or-more-axes linear motion actuator (51, 55, 56) which causes the link actuation device to advance and retract relative to the mount, and a one-or-more-axes linear motion actuator which causes a workpiece to advance and retract relative to the mount, the workpiece serving as a target to be subjected to welding work performed by the welding torch, wherein the welding torch is mounted to the distal end side link hub such that a leading end portion, of the welding torch, which performs welding work onto the workpiece faces the proximal end side and protrudes to the proximal end side relative to the proximal end side link hub.