A laminate body includes a plurality of dielectric sheets laminated together. A first ground conductor is provided in or on the laminate body. A second ground conductor is provided in or on the laminate body and located on a different layer from the first ground conductor. A signal line is provided between the ground conductors and with respect to a direction of lamination. A signal line is provided between the ground conductors and with respect to the direction of lamination and located closer to the second ground conductor than the signal line is, and the signal line has a portion extending along the signal line in a parallel-lines area when viewed from the direction of lamination. The first ground conductor has openings in the parallel-lines area, and the openings are arranged over the signal line when viewed from the direction of lamination.