The present invention relates to conductive metal nano particles and an nano-metal ink comprising the same, and more particularly, conductive metal nano particles comprising a metal and a hydrocarbon containing a carboxyl group, a production method thereof, a nano-metal ink comprising the conductive nano particles and a method for preparing printed circuit board using the nano-metal ink. According to the present invention, it is possible to laminate both the production of copper clad laminate (CCL) to bond a copper foil to a film and lithography process and simplify the production process by directly printing a wiring on a resin film in a single process and considerably reduce the manufacture cost and produce highly integrated and highly effective printed circuit board through miniaturization of line width in the printed circuit board. According to the present invention, in formation of a wiring on a flexible printed circuit board (FPCB) used in electronic appliances and electrical equipment such as mobile phones, PDA, notebook computers and the like or a wiring of a general appliance, the printed circuit board (PCB) or flexible printed circuit board (FPCB), metal nano-particles for forming the wiring is prepared, the metal nano-particles are converted into ink, which is then printed. The printed circuit board(PCB) or flexible printed circuit board IBPCB) prepared by a novel method is applied to electric and electronic appliances for industrial, official or house hold.