The invention provides a fitting mounted on one end of a glass tube (12) both ends of which are hermetically closed and one end of which has a remaining portion (38) of a gas discharge tube which remaining portion projects in the direction of a tube axis X. The fitting is formed in a closed-bottomed tubular shape with a tube section (42) and a bottom section (44) and has a fitting body (46) fitted on the one end and a pair of fitting pins (48, 50) raised from the fitting body (46). The fitting body (46) has a receiving section (52) projecting from the center of the bottom section (44) and receiving at least a portion of the remaining portion (38) projecting in ahammered-out shape in the direction of the tube axis X. The pair of fitting pins (48, 50) is raised from the bottom section (44), on both sides of the receiving section (52), so as to be in substantially parallel with the direction of the tube axis X.