A method of manufacturing nickel nanoparticles and nickel nanoparticles thus produced, having superior dispersion stability and smooth surface, by reducing after forming nickel-hydrazine complex in a reverse microemulsion, where the method includes forming an aqueous solution including nickel precursor, surfactant, and hydrophobic solvent, forming nickel-hydrazine complex by adding a reducing agent that includes hydrazine to the mixture, and producing nickel nanoparticles by adding a reducing agent to the mixture that includes the nickel-hydrazine complex.