A magnetoresistive effect device includes an input port, an input-side signal line, an MR unit including a magnetoresistive effect element and a magnetic-field generating signal line, and an output unit including a magnetoresistive effect element, an output-side signal line, and an output port. The magnetoresistive effect device further includes a DC application terminal. The magnetoresistive effect element is connected to the output port via the output-side signal line in the output unit. The input-side signal line is arranged so that a high frequency magnetic field generated from the input-side signal line is applied to the magnetoresistive effect element in the MR unit. In the MR unit, the magnetoresistive effect element is connected to the magnetic-field generating signal line. The magnetic-field generating signal line is arranged so that a high-frequency magnetic field generated from magnetic-field generating signal line is applied to the magnetoresistive effect element in the output unit.