Abstract: A heat pipe heat exchanger for transferring heat from a high temperature fluid such as, for example, exhaust gas of a boiler, to a low temperature fluid comprises a first flow path (13,14,15,16,17) along which the high temperature fluid flows, a second flow path (18,19,20,21,22) along which the low temperature fluid flows, and a rotor (28) formed by a plurality of heat pipes (8) disposed across the two flow paths with such intervals that the high temperature fluid or the low temperature fluid can pass therebetween and transferring heat from the high temperature fluid to the low temperature fluid, and the rotor (28) has a separating member (9) fixed to the rotor and separating the first flow path (14,15,16) therein from the second flow path (19,20,21) and is rotatable. By this, corrosion, decreased wall thickness and clogging of the heat pipes is prevented from being localized in a particular portion thereof and the maintenance work of the heat exchanger can be facilitated.