Abstract: An interrupting layer of inorganic powder other than diamond is formed on the surface of a substrate and a surface of the interrupting layer is contacted with excited raw material gases containing a carbon source, under conditions suited to depositing of diamond on the interrupting layer. The diamond which is synthesized is separated from the substrate. The use of the interrupting layer, composed of the inorganic fine powders, allows ready separation of the diamond from the substrate and the diamond separated is suitable for diaphragms for speakers, heat conductive plates, cutting tools, semiconductors, etc. by appropriately choosing shapes of the substrate. Further, the resulting diamond film can be pulverized, thereby yielding diamond powders which are useful for abrasive tools, cutting tools, etc.