[Objective] To provide a method and system for surely and conveniently generating plasma in a narrow tube having a small diameter. [Solution] The first electrode 30 formed by a conductive member covered with an insulator or dielectric is inserted into the narrow tube 10. The narrow tube 10 is located on the second electrode 20. The power supply 40 applies an alternating voltage or pulse voltage between the first electrode 30 and the second electrode 20 so that plasma is generated in the narrow tube 10 around the first electrode 20.
