The producing unit for continuously producing metal microparticles formed of a multicomponent alloy accompanied by the generation of a byproduct gas through an early reaction of the formation of the metal particles comprises a first mixing unit for continuously supplying and mixing a plurality of solutions for conducting the early reaction, a second mixing unit for continuously supplying another solution to the reaction liquid containing the metal microparticles formed in the early reaction and for mixing the two solutions, to introduce dissimilar metal atoms into the crystal lattices of the metal microparticles, and a gas-liquid separation unit that is installed in a midway of the pipe which is made so as to have enough length to finish the early reaction, and which continuously passes the reaction liquid to the second mixing unit from the first mixing unit, and that continuously removes the byproduct gas generated with the proceeding of the early reaction.