To provide a probe system in order to start and stabilize plasma discharge.

The probe system (10) includes an inside conductor (12) joined to an AC voltage source (14), an outside conductor (16) which is arranged around the inside conductor, and in which one end part is joined to the AC voltage source, and the other end part forms a first electrode (20), and a second electrode (22) which is separated from a first electrode by a cavity (24), and starts the plasma discharge in the cavity. An ultrasonic probe system (110) includes a carrier signal source (112) to supply an RF carrier signal, an acoustic modulator (116) to supply an envelope signal, a mixer (120) to mix the RF carrier signal and the envelope signal and to supply a modulated RF signal, and an RF plasma probe (124) which is separated from a ground electrode (126) by the cavity (128) and generates plasma to generate an ultrasonic wave in the cavity when receiving the modulated RF signal.