An apparatus for treating a substrate comprises a chamber having a treatment space for treating the substrate; a supporting unit which supports the substrate, inside the treatment space; a gas supplying unit which supplies process gas into the treatment space; and a plasma source which generates plasma based on the process gas inside the treatment space. The supporting unit comprises a supporting plate on which the substrate is placed; a focus ring which is disposed to surround the substrate supported by the supporting plate; a temperature control unit which adjusts a temperature of the focus ring. The temperature control unit may include a first heater which is disposed to heat the focus ring under the focus ring and to be opposite to the focus ring; and a cooling member which is provided under the first heater.