PURPOSE: To largely reduce man-hour of a cleaning operation by automatically cleaning sanitarily a rotor element of a rotary heat exchanger without irregularity.

CONSTITUTION: A gas injection nozzle 1 and a gas suction port 2 are respectively self-movably provided along guiding passages 5 and 6 by motors 3 and 4. The nozzle 1 is opposed to one air exit and entrance surface 1 of a rotary heat exchanger 10, and the passages 5 and 6 are radially movably fixed by guiding passage fixing means 8 and 9 while opposing the port 2 to air exit and entrance surface 12 of its opposite side. The motors 3 and 4 are controlled by control means 7 while rotating the exchanger 10 to be self-moved to move the opposed nozzle 1 and the port 2. Dust adhered to a rotor element 13 of the exchanger 10 is flown out by gas injected from the nozzle 1, and sucked from the port 2 to clean the element 13.