A magnetoresistance effect device includes first and second ports, first and second circuit units, and reference potential and DC applying terminals. The first and second circuit units respectively include first and second magnetoresistance effect elements and first and second conductors. In the second conductor, the positional relationship between first and second end faces respectively on the first and opposite conductor sides in the first magnetoresistance effect element with respect to a flowing direction of a direct current flowing inside the first magnetoresistance effect element and the positional relationship between first and second end faces respectively on the second and opposite conductor sides in the second magnetoresistance effect element with respect to a flowing direction of a direct current flowing in the second magnetoresistance effect element are opposite each other. The relative angle between the first and second circuit units in a predetermined cross product direction is 90 degrees or less.