To provide a waveguide-microstrip line converter manufacturable without complicating a manufacturing process, and having an airtight structure.

A dielectric substrate 104 comprises a plurality of laminated dielectric substrates. An antenna pattern 101 is formed in an inner layer of the dielectric substrate 104. A microstrip line 118 is formed on a surface layer of the dielectric substrate 104. A connection via 105 penetrates from the front face to the back face of the dielectric substrate 104 to connect the antenna pattern 101 to the microstrip line 118. Conductor patterns 119, 122 are connected to an upper housing 110 and a lower housing 111 sandwiching the dielectric substrate 104. A connection via 113 connects the conductor patterns 119, 122 on the front face and the back face of the dielectric substrate 104 to each other.