A method controls a portable welding robot to ensure good bead appearance even where a workpiece corner and a curved section of a guide rail are not located on a concentric circle and where there is a large difference in curvature between the workpiece corner and the curved section of the guide rail. A portable welding robot sets a guide rail with respect to a workpiece having a corner and performs arc welding on the workpiece while moving on the guide rail and a welding control device controls the portable welding robot. The control method includes determining a torch position on the workpiece via a torch position determination unit, calculating a torch angle at the torch position via a torch angle calculation unit, and controlling the torch angle via a movable part based on the calculated torch angle.