A discharge tube 17 of the present invention includes a glass tube 60 and ferrules 70 disposed around ends of the glass tube 60. Outer leads 61 for receiving power from an external power source project from ends of the glass tube 60. Each ferrule 70 includes a body 71 that is fitted onto the glass tube 60 and an insertion portion 73 that is disposed near the end of the body 71 and into which the outer lead 61 is inserted. The outer lead 61 includes a loop portion 62 at the end thereof. The outer lead 61 is electrically connected with the ferrule 70 when the loop portion 62 is inserted in the insertion portion 73.