Provided is a magnetoresistance effect device comprising a magnetoresistance effect element including a first ferromagnetic layer, a second ferromagnetic layer and a spacer layer and a high-frequency signal line. The high-frequency signal line includes an overlapping part disposed at a position overlapping the magnetoresistance effect element and a non-overlapping part disposed at a position not overlapping the magnetoresistance effect element in a plan view from a stacking direction. At least a part of the non-overlapping part is formed to be thicker than at least a part of the overlapping part. A distance in the stacking direction between a virtual plane including a surface on the side of the overlapping part of the first ferromagnetic layer and a center line in the high-frequency signal line in the stacking direction is shorter in at least a part of the overlapping part than in at least a part of the non-overlapping part.