To provide proper fixing force and excellent adhesion by imparting pressure or uniform displacement in the radial direction to a part or the whole of a tube end part changing in a plate thickness as it proceeds to the tube end or to the same part in a plate thickness as these.

An elastically deformable member 15 for imparting pressure or uniform displacement in the radial direction of a tube is used for a plate thickness gradually reducing part or the like. One end of the member 15 is positioned and sandwiched by a support material 11 so as to impart displacement to a prescribed position of a tube 7 to be fixed, the other end is sandwiched by the other support material 12a, and the initial sandwiching force is imparted via a screw 10a by a nut-shaped member 12 and a support material 10. Force for elastically deforming the member 15 is imparted by a movement of the support material 10, and in a moving method, a jack is fixed to the other end of the support material 10 by a nut via a tube plate pressing-down member, and high pressure liquid and gas are sent in. A moving distance can be adjusted by control of pressure, and highly accurate homogeneous fixing force can be obtained. A position required for adhesion and a fixation can be accurately decided.