A reduction gear for producing and feeding the rotation of a low pressure turbine driven by a combustion gas generated in a combustor to an output shaft is received in a central opening of a rotary type heat exchanger which is disposed so as to be perpendicular to a turbine shaft at a rear portion of a body housing of a gas turbine engine. As a result, not only the engine can be made small but also the output can be produced at to the opposite side of the heat exchanger. The combustor and a collector housing for collecting combustion gas are disposed on diametrical opposite sides in a transverse cross section of the body housing whereby an internal space of the body housing is effectively utilized and an axial dimension of the engine is shortened. Since the compressed air is supplied to the heat exchanger through peripheral walls of the body housing having a double construction, prevention of heat radiation from the body housing and effective utilization of an internal space of the body housing are realized.
