In the method of forming a multi-piled bump, metal balls can be stably and securely piled so as to form the multi-piled bump having a prescribed height. The method of the present invention comprises the steps of: holding a metal wire by a capillary; sparking and melting the wire so as to form metal balls; piling a plurality of the metal balls with applying a load and ultrasonic vibrations thereto, and characterized in that a tail length of the metal wire, which is held by the capillary, is controlled to make a gap between a center of the metal wire and a center of the metal ball one half of a diameter of the metal wire or less.