PROBLEM TO BE SOLVED: To provide a packaging unit providing a suitable interaction between half-shell members and a packaging material. SOLUTION: The packaging unit includes chain conveyers each having a plurality of jaws and a plurality of counter jaws, and the jaws and the counter jaws cooperate with each other to seal a tube using heating members mounted to the jaws. The conveyers are provided with half shell members 38 for controlling the capacity of a package. The half-shell members 38 are individually mounted to the jaws and the counter jaws whose movement contacting with and separating from the tube is controlled by guide means. The guide means have respective cams 44 for the chain conveyers and cam followers 42 mounted to the half-shell members are engaged with the cams 44, so that operations of the half-shell members are controlled. The cams 44 have adjustment devices to adjust distances between the cams 44, thereby adjusting the capacity of the formed package. COPYRIGHT: (C)2010,JPO&INPIT