Disclosed is a substrate treating apparatus which comprises a process chamber; an electrode configured to generate plasma from a gas supplied into the process chamber; an RF power supply configured to output an RF power; a transmission line configured to transmit the RF power to the electrode from the RF power supply; an impedance matching unit connected to the transmission line and configured to match plasma impedance; and a controller configured to output a control signal to the impedance matching unit, wherein the impedance matching unit comprises an adjustable capacitor having a plurality of capacitors and a plurality of switches corresponding to the plurality of capacitors, the plurality of switches being switched on/off according to the control signal so that capacitance of the adjustable capacitor is adjusted.