A magnetoresistive effect device includes at least one magnetoresistive effect element including a magnetization fixed layer, a spacer layer, and a magnetization free layer, a first port, a second port, a first signal line which is connected to the first port and through which high-frequency current corresponding to a high-frequency signal input into the first port flows, a second signal line, and a direct-current input terminal. The magnetoresistive effect element is arranged so that a high-frequency magnetic field occurring from the first signal line is applied to the magnetization free layer. The magnetoresistive effect element is connected to the second port via the second signal line. The direct-current input terminal is connected to the magnetoresistive effect element.