To ensure the reliability of high density and electric connection by a method wherein the tip of the squeezing device, where a prescribed roughened pattern is formed, is positioned on a plurality of bump electrodes, and each bump electrode is squeezed at the tip of the squeezing device.

The desired position of the flat surface of a levelling tool 50, which is a squeezing means, is set on the basis of the distance from the surface of a connection pad 3. Then, a wire bump 4 is connected to the prescribed position on the connection pad 3, the levelling tool 50 is moved down to the prescribed position which is set in advance, the pin-like protruding part 4A, which becomes the electrode of the wire bump 4, is pressure welded to the flat surface of the levelling tool 50, and a flat part 4AX is formed by squeezingly processing the protruding part 4A. At the same time, a plurality of diamond particles are pushed into the flat part 4AAX, and then a groove part 4AXG, corresponding to a plurality of diamond particles, is formed on the flat part 4AX of the protruding part 4A.