PURPOSE: To improve the durability of a supporting device for a rotary heat exchanger without dropping the key of the device even if a stress is applied to a buffer member disposed between the key and the key way of the device.

CONSTITUTION: The supporting device 10 of a rotary heat exchanger which heat exchanges low-temperature high-pressure gas with high-temperature low- pressure gas via a rotary heat storage rotor 1, has a key way 11 on the outer periphery of the rotor 1, and keys 13 engaged with the way 11 via a buffer member 12 and mounted on the inner periphery of a ring gear 2 disposed on the outer periphery of the rotor 1 via a spring 40, and comprises annular buffer members 12 provided on the entire peripheries of the keys 13 in such a manner that the members 12 are formed reversely rotatably to the rotating direction of the rotor 1 with respect to the way 11. As a result, even if a force for pressing out the key 13 from the way 11 is applied to the member 12 inserted between the key 13 and the way 11, there is no fear of dropping the member 12 from the key 13, thereby improving the durability of the device.