This magnetoresistance effect element includes a first ferromagnetic layer, a second ferromagnetic layer, and a non-magnetic layer. The non-magnetic layer is between the first ferromagnetic layer and the second ferromagnetic layer. The first ferromagnetic layer contains at least partially crystallized Heusler alloy containing Co. The non-magnetic layer has a first non-magnetic region and a second non-magnetic region. Each of the second non-magnetic region is sandwiched between the first non-magnetic regions in a thickness direction of the non-magnetic layer. Atoms or molecules constituting each of the second non-magnetic regions are smaller than atoms or molecules constituting the first non-magnetic region. Each crystal structure of the second non-magnetic region is a NaCl type structure. At least a part of the second non-magnetic region is crystallized continuously with the first non-magnetic region and the first ferromagnetic layer or the second ferromagnetic layer.