PURPOSE: To facilitate the separation of a sealing section by sealing a plastic tube with a sealing head with a projection to form a thin part at the center of the sealing section of the titled tube communicating with a blood bag or the like.

CONSTITUTION: First, a projection 4 is formed at the tip of a sealing head 3 of a tube sealer. Then, the sealing head 3 is used to clamp the plastic tube 1 communicating with a liquid storage container such as bag for transfusion of liquid or blood and after it is sealed by a high frequency heating or the like, a thin part 5 is formed at the center of a sealing part 2 of the tube 1.

EFFECT: As any cut part never be biased to the right or left of the sealing part, operation such as centrifugal separation can be done without breaking the sealing part.