PURPOSE: To facilitate butt welding of a tube stand and a tube and to make good welding by forming the tube stand by cutting an annular groove on the outer periphery of a tube hole pierced in a tube plate.

CONSTITUTION: Annular grooves 3 of specified depth are cut on the outer periphery of tube holes 4 from the outer face of a tube plate 2 in which many tube holes 4 are pierced, and a tube stand 5 having thickness almost equal to the thickness of a tube 1 is formed. The tube 1, such as heat transmitting tube for heat exchanger, etc. is attached to the tube stand 5 by welding 6. The depth of annular grooves 3, the sectional form and groove of the tube 1 are determined according to pitches of attaching of the tube 1 and methods of welding, etc. This tube assembling structure is easy to work and its cost can be reduced. As the thickness of the tube stand 5 and the thickness of the tube 1 are nearly equal, the heat capacity at the time of welding becomes nearly equal, and satisfactory butt welding can be performed.