A connecting structure of a waveguide converter includes a circuit substrate in which a hollow waveguide that propagates a high frequency signal is formed in a pierced manner; and an antenna substrate that is layered on the circuit substrate, and in which a converter that is arranged at a connecting point with the hollow waveguide and a strip line that extends from the converter and that propagates the high frequency signal are provided. A choke circuit to shield a leak of the high frequency signal is arranged around the hollow waveguide on a surface of the circuit substrate opposing to the antenna substrate so as to surround the hollow waveguide keeping a predetermined interval from the hollow waveguide, and the circuit substrate and the antenna substrate are fixed to each other by adhesive that is arranged at a position outside the choke circuit, between the substrates.