A gas discharge tube (1, 33, 37, 60, 89, 97) comprising a hermetically sealed container (2, 62) having a light exit window (4, 64) and a gas sealed in the container, a stem (5, 65) and first and second stem pins (9A, 9D) disposed in a standing position in the stem (5, 65) which is provided in said hermetically sealed container so as to extend in a tube axis direction, an anode portion (8, 68) and a cathode portion (20, 80, 5) electrically connected to the first and second stem pins (9A, 9D) respectively the tube being for causing discharge of predetermined light toward the outside from the light exit window (4,64) of the hermetically sealed container (2, 62) by generating a discharge between said anode portion and said cathode portion, said gas discharge tube further comprising: a first discharge path limiting portion (16,76,C4) disposed at a point on a discharge path between said anode portion and said cathode portion and having a first opening (18,78) for narrowing said discharge path; a second discharge path limiting portion (12,38,72, C5) disposed at a point on said discharge path between said first discharge path limiting portion and said anode portion and having a second opening (13,73) for narrowing said discharge path; a first electrical insulation portion (14,70) disposed between said first discharge path limiting portion and said second discharge path limiting portion; a second electrical insulation portion (10,67) on which the first electrical insulation portion is positioned and which is disposed on the anode portion side of the second discharge path limiting portion; characterised by further comprising a third stem pin disposed in a standing position in said stem so as to extend in said tube axis direction, the distal end part of which is electrically connected to said first discharge path limiting portion; a fourth stem pin disposed in a standing position in said stem so as to extend in said tube axis direction, the distal end part of which is electrically connected to said second discharge path limiting portion; and a light-emitting portion assembly (6, 66) comprising the first electrical insulation portion and the second electrical insulation portion, which assembly houses said anode portion, said cathode portion, said first discharge path limiting portion, and said second discharge path limiting portion, and which is supported by said first through fourth stem pins; wherein the distal end of the fourth stem pin is positioned between the first electrical insulation portion (14,70) and the second electrical insulation portion (10,67); and wherein the first electrical insulation portion (14,70) is in contact with the second discharge path limiting portion (12,38,72,C5) at a position between the distal end of the fourth stem pin and the first discharge path limiting portion (16,76,C4). a first discharge path limiting portion (16,76,C4) disposed at a point on a discharge path between said anode portion and said cathode portion and having a first opening (18,78) for narrowing said discharge path; a second discharge path limiting portion (12,38,72, C5) disposed at a point on said discharge path between said first discharge path limiting portion and said anode portion and having a second opening (13,73) for narrowing said discharge path; a first electrical insulation portion (14,70) disposed between said first discharge path limiting portion and said second discharge path limiting portion; a second electrical insulation portion (10,67) on which the first electrical insulation portion is positioned and which is disposed on the anode portion side of the second discharge path limiting portion; characterised by further comprising a third stem pin disposed in a standing position in said stem so as to extend in said tube axis direction, the distal end part of which is electrically connected to said first discharge path limiting portion; a fourth stem pin disposed in a standing position in said stem so as to extend in said tube axis direction, the distal end part of which is electrically connected to said second discharge path limiting portion; and a light-emitting portion assembly (6, 66) comprising the first electrical insulation portion and the second electrical insulation portion, which assembly houses said anode portion, said cathode portion, said first discharge path limiting portion, and said second discharge path limiting portion, and which is supported by said first through fourth stem pins; wherein the distal end of the fourth stem pin is positioned between the first electrical insulation portion (14,70) and the second electrical insulation portion (10,67); and wherein the first electrical insulation portion (14,70) is in contact with the second discharge path limiting portion (12,38,72,C5) at a position between the distal end of the fourth stem pin and the first discharge path limiting portion (16,76,C4).