To make the fluid flow in a tube turbulent and to obtain large heat exchange efficiency by spirally intertwining at least two tubular bodies and fixing these bodies to each other in this state.

The tube 10 is a copper tube comprising the two copper tubular bodies 11, 12 and the cross-sectional shape of their outside surfaces are formed to a circular shape. The two tubular bodies 11, 12 are spirally intertwisted and are press welded or fixed to each other in this state. The respective contact parts 11a, 12a of the two tubular bodies 11, 12 are press welded or fixed to each other in the state of maintaining tight contact with each other to render a good heat conductivity between the two tubular bodies 11 and 12. The tube is usable as a heat transfer tube to execute the heat exchange of the fluid tubes by passing respectively different fluids into the respective tubular bodies 11, 12. In such a case, the two tubular bodies 11, 12 are in the spirally intertwisted state to each other and, therefore, the fluid flow in the tube 10 is made turbulent and the large heat exchange efficiency is obtd.