The magnetoresistive effect element unit includes an anisotropic magnetoresistive effect element and a conductive reset line that, as viewed in a direction orthogonal to both a magnetic sensing direction x′ and an easy magnetization direction y′ of the anisotropic magnetoresistive effect element, passes through a center of the anisotropic magnetoresistive effect element, extends in a direction inclined from the easy magnetization direction y′ so as to form an angle of 45° or less with the easy magnetization direction y′, and is parallel to a plane including the magnetic sensing direction x′ and the easy magnetization direction y′. As viewed in the direction orthogonal to both the magnetic sensing direction x′ and the easy magnetization direction y′, the reset line has a width that covers an entirety of the anisotropic magnetoresistive effect element.