PURPOSE: To break the tip part of an outer tube without deteriorating the outer tube, and facilitate the attachment and the detachment of the outer tube by holding the outer tube so that it can be attached and detached and so that the tip part is located on the vacuum exhaustion side, and breaking the tip part by moving a tip-part breaking member perpendiclarly to the axial direction of the tip part.

CONSTITUTION: An outer tube 14 is held so that a tip part 17 slightly protrudes inside a vacuum container 25 by inserting a neck part 24 of the tube 14 into a chuck 26. Next, after the container 25 is vacuumed to a given degree, and a valve 33 is closed, a rotary introduction terminal 30 is rotated in the direction indicated by the arrow so as to rotate a tip-part breaking member 32 horizontally through a vertically driving shaft 31. Next, the member 32 is moved downward with the shaft 31 until the member 32 corresponds to the tip part 17 so as to give the part 17 a downward force which is perpendicular to the axis of the part 17 by making the member 32 in contact with the part 17. As a result, the part 17 is broken, and gas charged in the outer tube 14 is introduced into a vacuum container 25. After that, measurement of the pressure of gas charged in the container 25, and collection of the charged gas are performed with proper means with which the container 25 is equipped.