Disclosed is a substrate treating apparatus. The substrate treating apparatus includes a chamber having a treatment space in the interior thereof, a support unit configured to support a substrate in the treatment space, a gas supply unit configured to supply a gas into the treatment space, and a plasma generating unit configured to generate plasma from the gas, wherein the support unit includes an electrostatic chuck including an upper body having a support surface that suctions the substrate and a lower body extending from the upper body to a lower side, wherein the lower body has an extension part extending laterally from the upper body, a focus ring disposed on the extension part of the electrostatic chuck, and a metallic ring provided between the upper body of the electrostatic chuck and the focus ring and configured to control plasma in an extreme edge of the substrate.