A magnetoresistance effect device includes a magnetoresistance effect element including a magnetization fixed layer, a magnetization free layer of which a direction of magnetization is changeable relative to a direction of magnetization of the fixed layer, and a spacer layer sandwiched between the fixed and free layers, a first signal line configured to generate a high frequency magnetic field when a high frequency current flows and apply the field to the magnetization free layer, and a DC application terminal configured to be capable of connecting a power supply for applying a DC current or voltage in a stacking direction of the element, and the element is disposed with respect to the terminal so the DC current flows from the fixed layer to the free layer in the element or so the DC voltage at which the magnetization fixed layer is higher in potential than the magnetization free layer is applied.