A plasma generation system and related method for generating plasma in a cavity of a narrow tube, the system including: a first electrode including a conductive member covered with an insulator or dielectric, the first electrode being inserted into the cavity of the narrow tube to generate the plasma; a power supply to apply an alternating voltage or pulse voltage to the first electrode; and a second electrode located outside the narrow tube and connected to the power supply, the power supply applying the alternating voltage or pulse voltage between the first electrode and the second electrode, wherein the conductive member is made of a wire, a portion of the narrow tube is provided between the first electrode and the second electrode, and the second electrode is arranged and shaped so that a discharge is unevenly performed in a circumferential direction of the first electrode.