The method of the present invention provides a magnetoresistance effect element, which is capable of having a high MR ratio, corresponding to high density recording and being suitably applied to a magnetoresistance device even though a barrier layer is thinned to reduce resistance of the magnetoresistance effect element. The method of producing the magnetoresistance effect element, which includes the barrier layer composed of an oxidized metal, a first magnetic layer contacting one of surfaces of the barrier layer and a second magnetic layer contacting the other surface thereof, comprises the steps of: laminating the barrier layer on the first magnetic layer with using a target composed of the oxidized metal; and laminating the second magnetic layer on the barrier layer. The barrier layer is annealed before laminating the second magnetic layer thereon.