A high-frequency signal line includes a dielectric body including a first dielectric layer and one or more other dielectric layers laminated together. A first signal line is provided on a first main surface, which is a main surface located on one side in a direction of lamination, of the first dielectric layer. A second signal line is provided on a second main surface, which is a main surface located on another side in the lamination direction, of the first dielectric layer so as to face the first signal line via the first dielectric layer. The second signal line is electrically connected to the first signal line. A first ground conductor is located on one side in the lamination direction than the first signal line. A second ground conductor is located on another side in the lamination direction than the second signal line.