Abstract: There is provided an adaptive plasma source, which is arranged at an upper portion of a reaction chamber having a reaction space to form plasma and is supplied with RF (radio frequency) power from an external RF power source to form an electric field inside the reaction space. The adaptive plasma source includes a conductive bushing and at least two unit coils. The bushing is coupled to the RF power source and arranged at an upper central portion of the reaction chamber. The at least two unit coils are branched from the bushing and surround the bushing in a spiral shape and have the number of turns equal to a×(b/m), where a and b are positive integers and m is the number of the unit coils.