The magnetoresistance effect device includes: a first port; a second port; a magnetoresistance effect element; a first signal line that is connected to the first port and applies a high frequency magnetic field to the magnetoresistance effect element; a second signal line that connects the second port and the magnetoresistance effect element to each other; and a direct current application terminal capable of being connected to a power supply that applies a direct current or a direct current voltage. The first signal line includes a magnetic field generator, which extends in a first direction, at a position in the lamination direction of the magnetoresistance effect element or an in-plane direction that is orthogonal to the lamination direction, and the magnetic field generator and the magnetoresistance effect element include an overlapping portion as viewed from the lamination direction in which the magnetic field generator is disposed, or the in-plane direction.