To provide a waveguide coupler which simplifies connection work or the like for the waveguide terminals of dielectric substrates with a high frequency circuit formed thereon and attains the reduction of the cost.

The GND surface 8a of a waveguide terminal 2a of a dielectric substrate 1a and the GND surface 8b of a waveguide terminal 2b of a dielectric substrate 1b are connected by solders 7a. The solders 7a are disposed around the waveguide terminals 2a, 2b. In a case 20 formed of a metal, a waveguide terminal 2c is disposed while facing the waveguide terminal 2b. The dielectric substrate 1b and the case 20 are fixed by adhesion or screws.