Abstract: The double tube for heat exchange includes: a spiral pipe having ridges and valleys alternately formed on a circumferential surface along a spiral track thereof and guiding a first fluid therethrough; an outer pipe receiving the spiral pipe axially inserted thereinto and guiding a second fluid along the circumferential surface such that the second fluid exchanges heat with the first fluid; a resistance member protruding from the spiral pipe or valleys to increase time of the second fluid in the valleys and to support the ridges adjacent thereto. Unlike typical double tubes, this double tube can: improve heat exchange efficiency by virtue of the spiral pipe; improve flow directionality of the second fluid; reduce noise through expansion of a space between an end joint of the outer and inner pipe to reduce the pressure of the second fluid; and improve efficiency through resistance members protruding from the valleys.