A high-frequency signal line includes an element assembly including a plurality of insulator layers, a linear signal line provided in or on the element assembly, a first ground conductor provided in or on the element assembly and extending along the signal line, and a plurality of floating conductors provided in or on the element assembly on a first side in a direction of lamination relative to the signal line and the first ground conductor, so as to be arranged along the signal line in an orientation crossing the signal line when viewed in a plan view in the direction of lamination. The floating conductors are opposite to the signal line and the first ground conductor with at least one of the insulator layers positioned therebetween, the floating conductors being connected to neither the signal line nor the first ground conductor. A capacitance is created between the first ground conductor and each of the floating conductors, and has a greater value than a capacitance created between the signal line and the floating conductor.