A method for producing metal nanowire of small diameter and long length. In the method for producing a metal nanowire, a first solution containing an ionic derivative and a polyol as a solvent are kept at 80-200° C., and a second solution containing a metal salt and a polyol as a solvent is supplied into the first solution so that the ratio between the number of moles of metal atoms in the metal salt supplied in one minute and the total number of moles of halogen atoms in the ionic derivative in the first solution (the number of moles of metal atoms in the metal salt supplied in one minute/the total number of moles of halogen atoms in the ionic derivative) is less than 10. It is preferable that the ionic derivative is a quaternary ammonium halide and the metal salt is silver nitrate.