The present invention relates to composite metallic ultrafine particles which have excellent dispersion stability and can be produced on an industrial scale, and a process for producing the same, and a method and an apparatus for forming an interconnection with use of the same. The configuration of the conveying device permits airtight packaging of the material and is designed according to a principle that is very similar to the paternoster conveying principle. A thickness of the boss is made large at around a front end side of the blade on which the largest stress is applied. An annular space arranged around the cylinder is provided as part of the oil returned to the oil supply tank.