The present invention relates to a processing method of wire material and a processing device therefor at the times of intending to make the tip of wire materials such as guide wire for catheter thin and flexible by tapering.When the wire material passes through the electrolytic tub, the wire speed is made constant and the current value is controlled, or the current value is made constant and the wire speed is controlled to give the processings such as tapering. For the electrolytic polishing bath, it is desirable to use a mixed bath comprising trivalent alcohol, perchloric acid and monovalent alcohol.The inventive method exerts an effect that the tapering can be given efficiently and yet with high precision compared with the traditional method of mechanical polishing or the method of dipping one by one batchwise into the electrolytic polishing bath.