The present invention relates to a method for forming a metal nanowire or a metal nanomesh. More particularly, the present invention relates to a method for forming a metal nanowire or a metal nanomesh capable of forming a variety of metal nanowires or metal nanomeshes in a desired shape by a simplified method.The method for forming a metal nanowire or a metal nanomesh includes the steps of forming a block copolymer thin film on a substrate, in which the block copolymer thin film includes specific hard segments and soft segments containing one or more polymer repeating units selected from the group consisting of a poly(meth)acrylate-based repeating unit, a polyalkylene oxide-based repeating unit, a polyvinylpyridine-based repeating unit, a polystyrene-based repeating unit, a polydiene-based repeating unit and a polylactone-based repeating unit; conducting orientation of the hard segments and soft segments in a lamellar or cylindrical form in the block copolymer thin film; selectively removing the soft segments; adsorbing a metal precursor onto the hard segments; and removing the hard segments.