There are provided an apparatus and method for processing a substrate. By using the apparatus and method, plasma processing can be individually performed on each of edge and rear regions of a substrate in a single chamber. The apparatus includes a chamber providing a reaction space; a stage installed in the chamber; a plasma shielding unit installed opposite to the stage in the chamber; a support unit for supporting a substrate between the stage and the plasma shielding unit; a first supply pipe provided at the stage to supply a reaction or non-reaction gas to one surface of the substrate; and second and third supply pipes provided at the plasma shielding unit, the second supply pipe supplying a reaction gas to the other surface of the substrate, the third supply pipe supplying a non-reaction gas to the other surface.