The objective of this study is to realize a manipulator of 0.5 mm in outside diameter as a part of 'research and development of micro machine technology.' This manipulator is intended as a part of a working robot to fix or observe the inside wall of a small pipe. One of the important problems of this research is to establish a processing method of a tubular small structure. MIM, metal injection molding, has been adopted to fabricate such a small structure. As a processing method to machine small molds for MIM, finish processing with surface roughness of Rmax 0.1 µm has been under our research applying 'vibrational processing technology,' which was developed on our own. This paper presents the results of 'vibrational processing technology' surface finishing of molds for metal injection.