A substrate treating apparatus includes a process chamber configured to perform plasma treatment, a substrate support in a lower portion of the process chamber and configured to support a substrate, a showerhead in an upper portion of the process chamber and configured to supply a process gas for the plasma treatment toward the substrate, and a baffle surrounding the substrate support. The substrate support functions as a first electrode for generating plasma, the showerhead and the baffle function as a second electrode for generating the plasma, the baffle has a variable height, and an area of the second electrode varies as a height of the baffle varies.