A dielectric body includes a first radiating element on a first side and a second radiating element on a second side. The first radiating element and the second radiating element are linear conductors that each extend from a first end to a second end (an open end), and are parallel or substantially parallel to each other in a direction from the first end to the second end. The first end of the first radiating element is connected to a first port of a coupling degree adjustment circuit, and the first end of the second radiating element is connected to a second port of the coupling degree adjustment circuit. The first radiating element and the second radiating element are mainly coupled to each other in the coupling degree adjustment circuit.