A high-frequency signal transmission line includes a body; a signal line including a first line portion provided to a first layer of the body, a second line portion provided to a second layer of the body alternately being connected; and a first ground conductor provided to the first layer or a third layer positioned on an opposite side of the second layer relative to the first layer, and also overlaid with a plurality of second line portions in planar view from a normal direction of a principal surface of the body, and also not overlaid with a plurality of the first line portions. A property impedance of the first line portion and a property impedance of the second line portion are different from each other.