Produce metal particles offering high purity and uniform granular shape and size: by forming a combustion chamber comprising an injector nozzle for mixture gas of oxygen and hydrogen, an ignition device and a material metal feeder in the upper space of a high-pressure water tank filled with inert gas; igniting inside the combustion chamber via the ignition device the injector nozzle for mixture gas of oxygen and hydrogen and melting (vaporize) the material fed by the material metal feeder; and then causing the produced molten metal droplets to contact high-pressure water and let the resulting metallic particles to precipitate in water.