Abstract: Herein disclosed is a dual-tube heat pipe type heat exchanger comprising a heat pipe confined with a working fluid for transferring a heat as a latent heat by repeating evaporations and condensations. The heat pipe includes an outer tube which is disposed within a hot fluid such that its axis is generally horizontal. Further included is an inner tube which is inserted in the outer tube and radially offset upward to substantially contact with the top portion of the inner face of the outer tube and to confine a space between the inner circumference of the outer tube and the outer circumference of the inner tube, thus forming the heat pipe.