The present invention relates to a method for manufacturing metal nanoparticles, more particularly to a method for manufacturing metal nanoparticles, which includes: preparing a mixed solution including capping molecules, a metal catalyst, a reducing agent, and an organic solvent; adding a metal precursor to the mixed solution and raising to a predetermined temperature and stirring; and lowering the temperature of the mixed solution and producing nanoparticles. Embodiments of the invention allow the synthesis of nanoparticles, such as of single metals, metal alloys, or metal oxides, to a high concentration in a water base using a metal catalyst.