A TIG welding device (10) includes a welding robot (11), robot control device (12), welding torch (13), welding control device (14), gas feeder (15), and a height detection device (16). The welding torch (13) is set at a reference position, and the height detection device (16) detects the respective heights of two tip parts (4e). The robot control device (12) drives the welding robot (11) such that a torch electrode (13c) of the welding torch (13) abuts on central part of the higher tip part (4e). When the torch electrode (13c) is moved toward the reference position while power is supplied to the torch electrode (13c), and inert gas flows in the periphery of the torch electrode (13c), arc (AC) is generated in a gap between the tip parts (4e) and the torch electrode (13c). The overall two tip parts (4e) are melted and welded by this arc (AC).