To provide the structure at a low cost by simplifying the heat radiating structure so as to reduce the limitation to the design in the heat radiating structure of a waveguide isolator in a microwave circuit for a satellite mounting equipment.

A heat radiating bracket 2 is directly mounted to an absorbing body 4 and the heat radiation bracket 2 acts like a radiator to radiate heat to a satellite shell without screw fastening to the satellite shell 6. Furthermore, in order to prevent a temperature rise of the absorbing body itself, a projection (male part) is provided in the heat dissipation bracket 2 and fitted to a recess (female part) provided to the absorbing body so as to deliver the internally generated heat of the absorbing body to the heat radiating bracket 2 efficiently.