A method for manufacturing metal nanoparticles, the method including forming a mixture by dissociating a metallic salt of a metal selected from the group consisting of Ag, Pd, Pt, Au and an alloy thereof as a metal precursor in fatty acid; and adding a metallic salt of a metal selected from the group consisting of Sn(NO.sub.3).sub.2, Sn(CH.sub.3CO.sub.2).sub.2, and Sn(acac).sub.2 as a metallic catalyst into the mixture and mixing the mixture and the metallic salt. According to the method, metal nanoparticles have a uniform particle size distribution and a high yield by performing in a non-aqueous environment without using any organic solvent, and are environmentally friendly due to no use of a reducing agent.