A method for processing a work piece including a magnetic material and a method for manufacturing a magnetic recording medium. With the use of these methods, the magnetic recording medium with fine magnetic properties, magnetic recording and reproducing equipment, and the like are efficiently manufactured by processing the work piece including the magnetic material by use of an oxidizing reactive gas and then certainly removing the oxidizing reactive gas. An NH3 gas (a non-oxidized gas including hydrogen elements) is used as a cleaning gas. The cleaning gas is turned into plasma, and then a work piece is dry cleaned by use of the cleaning gas.