PURPOSE: To prevent the generation of an unnecessary interference fringe having an adverse effect on a beam pattern owing to the breaking of the inside diametral section of the ends of a glass capillary and the diffraction of laser beams by a broken section when a laser tube is manufactured by smoothly heating and forming the inside diametral sections of both ends of the glass capillary in the He-Ne laser tube in a tapered shape.

CONSTITUTION: A pair of mirrors 1A, 1B for an optical resonator are fixed to metallic-mirror support paired parts 3A, 3B mounted at both ends of a glass bulb 2 forming a package respectively. In a glass capillary held to the package 2, one end is retained on one side of the glass bulb, and a discharge path is formed among a cathode pin 5 and a cathode component 6 and the one metallic- mirror support paired component 3B functioning as an anode electrode in combination. Since inside diametral sections on both ends of the glass capillary 4 are heated and formed smoothly in a tapered shape, the inside diametral sections are not broken when a laser tube is manufactured, and no glass chip is generated, thus preventing the generation of unnecessary diffraction, etc., having an adverse effect on the beam pattern of laser beams.