To absorb an abnormal vibration even if the vibration is generated by oscillatorily supporting one motor for driving two rotors of a rotary heat exchanger to a specific position, and cooperatively rotating the rotors via an endless belt at a driving pulley on a rotary shaft of the motor.

Rotors 21, 22 are aligned vertically in rows and contained in a space surrounded by an upper frame 11, a bottom frame 12 and longitudinal frames 13, 14, and rotatably supported. A shaft 34 is disposed in a longitudinal frame 13 separate at an equal distance from the rotary shafts in parallel with the rotary shafts of the rotors 21, 22, and four guide shafts 36 are stood on a support base 35 oscilpatorily supported by the shaft 34. A driving pulley 52 is fixed to an output shaft 51 of a motor 31 on a motor support plate 38 floatably supported to the shafts 36 via a spring to rotate the rotors 21, 22 via endless belts 53, 54 by rotatably driving.