A plasma stabilizer having a circuit for measuring the electron temperature and electron density of a plasma by a triple probe, a circuit for controlling the plasma pressure and a circuit for controlling the power for exciting a plasma. A stable plasma is generated automatically by controlling automatically at least one of the plasma pressure and the power for exciting the plasma. In a conventional high frequency plasma device, since the high frequency or microwave power and the gas pressure are adjusted manually, the device cannot follow up the variations of the power and pressure automatically.
