An RF supply system is to be connected to an RF electrode disposed outside or inside a process chamber to assist a plasma process performed in the process chamber. This system includes an RF power supply, a matching unit, and an impedance converter. The RF power supply is configured to supply an RF power for plasma generation to the electrode through a transmission path. The matching unit is disposed on the transmission path between the RF power supply and the electrode, and configured to match a load impedance viewing from the RF power supply with an impedance of the RF power supply side. The impedance converter is disposed on the transmission path between the matching unit and the electrode, and configured to convert a load impedance viewing from the matching unit to an impedance higher than an actual impedance on the electrode side.