A magnetoresistance effect element has an underlayer, a first ferromagnetic metal layer, a second ferromagnetic metal layer, and a tunnel barrier layer that is sandwiched between the first and second ferromagnetic metal layers. The tunnel barrier layer has a spinel structure and includes at least one lattice-matched portion, and at least one lattice-mismatched portion. The underlayer is made of a nitride layer; a layer having a (001)-oriented tetragonal or cubic structure; or a layer having a stacked structure with a combination of a nitride layer having a (001)-oriented NaCl structure and a layer having a (001)-oriented tetragonal or cubic structure.