An object of this invention is to provide a manufacturing method of metal nanowire in which a length and a diameter can be uniformly controlled, metal nanowire having excellent form uniformity, and a transparent electric conductor exhibiting excellent conductivity and transparency by employing metal nanowire having excellent conductivity and transparency. A manufacturing method of metal nanowire which reduces a metal ion in a solution to form metal particles having a wire-form, wherein a nucleus forming process and a particle growth process after said nucleus forming process are provided, and said nucleus forming process reduces a metal ion to form reduced metal, which is directly precipitated on the surface of said particles formed in the said nucleus forming process or on the surface of particles having grown from said nucleus particles during a growth process, whereby metal particles are formed.