PURPOSE: To provide a rotary heat exchanger, facilitated in the assembling works as well as the mounting works of the rotor element thereof at site.

CONSTITUTION: In a rotary heat exchanger 1, effecting heat exchange between discharging air and supplying air by rotating a rotor element 11 arranged across an air discharging duct 2 and an air supplying duct 3 which are provided in parallel, a travelable trestle 10, insertable into both of the air discharging duct 2 and the air supplying duct 3 across the inner parts of both ducts, is provided while the trestle 10 is provided with the rotor element 11, a driving means 14, driving the rotation of the rotor element 11, and a sealing member, sealing the leakage of air in the air discharging duct 2 as well as the air supplying duct 3 through the surface of the rotor element 11.