An apparatus and a method for controlling a welding robot is disclosed. In the method, an initial welding is performed under initial welding conditions while moving a welding object and a welding torch relatively to each other along a predetermined welding line. Then, a change point at which at least one of the welding conditions should be changed, and a change value of the welding condition, are determined. The welding conditions are changed to the change value at the change point while the welding operation and the relative movement of the welding object and the welding torch are continued. Thus, the welding operation is not stopped during the real-time change of the welding conditions such as welding voltage, welding current, welding speed and the like. Thus, working efficiency and the welding quality are improved, and the discontinuity of the welding bead does not occur.