There is provided a process comprising mixing a divalent copper oxide with a reducing agent in the presence of a complexing agent and a protective colloid in a liquid medium to thereby produce copper microparticles without formation of a univalent copper oxide from the divalent copper oxide. Further, there is provided a process comprising reducing a divalent copper oxide in the presence of a complexing agent and a protective colloid, such as a protein, to thereby form metallic copper microparticles, adding a protective colloid scavenger, such as a protease, to thereby remove the protective colloid and effect agglomeration of metallic copper microparticles, and filtering the mixture by means of a pressure filter, a vacuum filter, a suction filter, etc.