A magnetoresistance effect element is capable of realizing a high magnetoresistance (MR) ratio. The magnetoresistance effect element includes a laminate in which: an underlayer; a first ferromagnetic metal layer; a tunnel barrier layer; and a second ferromagnetic metal layer are laminated in that order. The underlayer is made of a nitride, the tunnel barrier layer is made of any one selected from a group consisting of MgAl2O4, ZnAl2O4, MgO, and γ-Al2O3, and a degree of lattice mismatching between a lattice constant of the tunnel barrier layer and a lattice constant of a crystal structure to be taken by the underlayer is 5% or less.