Provided is a production method for a magnetoresistive element including treating a stacked layer into a predetermined shape. The stacked layer includes a magnetoresistive layer whose resistance changes depending on a magnetic field and a cap layer above the magnetoresistive layer and having a thickness in a range of 10 nm to 60 nm. The method further includes covering and protecting the stacked layer with an insulating layer, forming an opening in the insulating layer by reactive etching and exposing a surface of the cap layer at the opening, etching the cap layer in a range less than a total thickness of the cap layer by ion milling of the surface, and depositing an upper layer to be a part of the magnetoresistive element. The upper layer is in contact with the surface of the cap layer after the etching.