Provided is an apparatus for treating a substrate. The substrate treating apparatus includes a substrate supporting unit for supporting the substrate and fixing the substrate with electrostatic force, a plasma generating unit for generating a discharging plasma for discharging a charge of the substrate, and a power supplying unit for supplying power to the substrate supporting unit and the plasma generating unit, wherein the power supplying unit supplies power of a fluctuating pattern to the plasma generating unit when a charge of the substrate is discharged.