This invention provides a production process in which in a process for producing a magnetoresistive effect element, noble metal atoms in a re-deposited film adhered to a side wall after element isolation are efficiently removed to prevent short-circuiting due to the re-deposited film.The noble metal atoms are selectively removed from the re-deposited film by applying an ion beam, formed using a plasma of a Kr gas or a Xe gas, to the re-deposited film formed on the side wall of the magnetoresistive effect element after the element isolation.