A method by which ceramic nanowires with diameters ranging from several to several tens of nanometers can be synthesized with improvements in the shape retention of the nanowires and the yield of conversion to ceramic, which method comprises the steps of forming a thin film of a silicon-containing polymer usable as a ceramic precursor, irradiating the thin film with ion beams to form cylindrical crosslinked portions, extracting the un-crosslinked portions with a solvent to produce nanowires of the silicon-containing polymer, irradiating the nanowires with an ionizing radiation so that they are crosslinked again, and firing the re-crosslinked nanowires.