PURPOSE: To achieve small size the simple constitution, by using the microwave choke circuit of micro strip line form for the waveguide circuit including the microwave solidstate element.

CONSTITUTION: The opening absent for the said H wall surface of the rectangular waveguide 7 where one H wall surface is removed, is covered with the grounding plate 14 of the microstrip line and they are bonded. At the location where the solidstate element 11 mounted, a through-hole through which the tip 12 of the package of pill prong type of the solidstate element 11 can be inserted, is provided, and the tip 12 of the package of the solidstate element 11 is inserted to the small hole 13. The tip 12 of the package of the solidstate element 11 inserted to the small hole 13 is electrically connected to the strip conductor of the low pass filter circuit pattern. As the low pass filter circuit pattern, circular pattern or strip pattern are available.