A high-frequency device includes a substrate including a plurality of layers that are stacked on top of one another and that include dielectric and magnetic layers, terminals, pattern conductors each formed on one layer, and via conductors each extending through one layer. The pattern conductors and via conductors connect the terminals and form a signal line that transmits a high-frequency signal. A first portion of the signal line includes a via conductor extending through one magnetic layer and/or a pattern conductor sandwiched between two magnetic layers and has a predetermined resistance to the high-frequency signal. A second portion of the signal line includes a capacitor formed of two pattern electrodes with at least one dielectric layer and no magnetic layers sandwiched there between and/or an inductor including a pattern conductor formed on a dielectric layer. The high-frequency device has an impedance to the high-frequency signal at the terminals.