An apparatus and method for treating a thin film on a substrate is presented. The substrate is loaded on a fixed stage adapted to receive the substrate. An energy source is aligned through a space in a gas shield so as to face a thin film on the substrate to be repaired after the substrate is loaded. A protective insulating layer is removed by radiation from the energy source, a reaction gas is supplied to the space, and an open and/or short circuit in the thin film is repaired. The energy source and/or gas shield is moved during the repair, rather than the stage. If the energy source and gas shield are both moved, they are moved in opposite directions, either independently or dependent on each other, by first and second operating units, respectively.