PURPOSE: To obtain good joining of a tube and tube plate and improve work efficiency by inserting an elastic body into the tube and pressing the elastic body in axial direction from both ends.

CONSTITUTION: An elastic body 5 is inserted into a tube 3 corresponding to the joining part with a tube plate 2 and the end of the tube 3 is closed with a fixed board 6. When force is applied in the direction of the arrow by a pressure rod 4, the elastic body 5 is compressed and swelled out in radial direction, and expands the tube 3 to fit it to the hole of the tube plate 2. This method allows plural operations at a time and improves work efficiency.