To very easily and inexpensively manufacture an alloy or an intermetallic compound conventionally difficult to work by applying a removal treatment of a coated metal after applying a diffusion heat treatment to a fine wire made from the alloy or the intermetallic compound.

Plural holes are opened in e.g. Cu (metal A) ingot 1, things wound a Ti (metal B) bar with a single Nb (barrier) foil 3 are inserted into them one by one, a Cu lids are fitted onto both end surfaces of a Cu ingot 1 to seal, this billet is hot extruded and cold drawing is applied, whereby a composite multi-core wire is made. Further, after applying the diffusion heat treatment to it at 700°C for five hours, Cu (metal A) is dissolved to remove with nitric acid, whereby a great number of CuTi intermetallic compound fine wires are obtained. By this way, alloy fine wires, suitable for a heat resistant textile material and a filter material or the like and difficult to work, are easily manufactured.