To miniaturize a device, and to reduce the manufacturing cost by a simple device by inserting an outer tube into an inner tube to make a double tube, and relatively moving a heating/cooling device to heat/cool an outer circumference of the outer tube in the axial direction of the tube.

In a condition where an inner tube 1 is connected to an outer tube to make a double tube, a heating/cooling device 5 is moved on a rail from an end of the outer tube 2, the outer tube 2 is heated, and then, cooled. When the heated part is cooled, the thermal strain becomes a negative value, and the outer tube 2 on this part is contracted. By repeating the heating and cooling, the outer tube 2 is contracted to obtain the double tube.