A magnetoresistance effect element is provided in which a MR ratio is not likely to decrease even at a high bias voltage. A magnetoresistance effect element according to an aspect of the present invention includes: a first ferromagnetic metal layer; a second ferromagnetic metal layer; a tunnel barrier layer that is provided between the first ferromagnetic metal layer and the second ferromagnetic metal layer, in which the tunnel barrier layer is formed of a non-magnetic oxide having a cubic crystal structure represented by a compositional formula A1-xA′xO (A represents a divalent cation, and A′ represents a trivalent cation), a space group of the crystal structure is any one selected from the group consisting of Pm3m, I-43m, and Pm-3m, and the number of A ions is more than the number of A′ ions in a primitive lattice of the crystal structure.