PURPOSE: To enable effective removal of dust from the whole surface of a heat transfer wall.

CONSTITUTION: A swing arm of an upper support body effects a circular-arc motion like a pendulum around a bearing 14 as the center of rotation, in the longitudinal direction 13 of a passage of an exhaust gas, by a drive motor 12 through the intermediary of a gear reduction mechanism 9 and a link mechanism 11 connected to the end part of a shaft 10. A swing arm 14 of a lower support body effects a circular-arc motion like the pendulum around a bearing 16 as the center of rotation, in the longitudinal direction of the passage of the exhaust gas, in synchronous linkage with the swing arm of the upper support body through the intermediary of a link mechanism 15 fitted to the shaft 10 of the upper support body. Chain lines 18 joined to an upper support rod 17 of the upper support body are provided in extension through passages 20 of a heating fluid of a plate type heat exchanger 19 which makes the heating fluid and a fluid to be heated pass alternately through passages being adjacent to each other, and they are joined to a lower support rod 21 of the lower support body.