A tandem arc welding device in which the welding conditions and a program describing contents of operation are treated as independent to each other. It handles the welding conditions altogether simply as those parameters for the fore-going welding and those parameters for the hind-going welding. By so doing, a program can be produced without taking which of the two welders will become fore-going into consideration. Furthermore, a program and welding conditions thus provided offer superior re-usability and reproducibility to the tandem arc welding.