A method to determine welding conditions includes relational expressions or tables about various parameters for setting welding conditions. The method can determine and display the recommended values for the welding conditions which are suitable for the information about the object to be welded and the information about the welding method set by the operator. The welding conditions include a welding current, a welding voltage, a wire feed speed, a welding speed, and a leg length. Furthermore, if the operator changes the recommended value for a welding condition to a new value, the method can determine new recommended values for the other welding conditions compatible with the new value and display the new recommended values.