A plasma source is provided. The plasma source includes a chamber body, a supply passage, a vacuum connector, an antenna, a first insulator, a second insulator, and a conductor. The chamber body has an opening for emitting ions or electrons. The supply passage penetrates through a first peripheral wall of the chamber body. The vacuum connector is provided in a second peripheral wall of the chamber body at a position opposed to the opening. The antenna has a base end connected to the vacuum connector, and extends inside the chamber body toward the opening. The first insulator covers a first region of the antenna at a distal end of the antenna inside the chamber body. The second insulator covers a second region of the antenna at the base end of the antenna inside the chamber body. The conductor covers the second insulator.