A nanometer-size-particle production apparatus is provided which can prevent the occurrence of waste fluids, and which makes quick and continuous syntheses feasible while suppressing damages to the electrode.The present invention is a nanometer-size-particle production apparatus for synthesizing nanometer-size particles in a liquid by means of plasma in liquid, and comprises: a container for accommodating the liquid therein; an electromagnetic-wave generation device for generating a high-frequency wave, or a microwave; an electrode conductor whose leading end makes contact with the liquid to supply the high-frequency wave or the microwave to the liquid; a covering portion being disposed into the liquid so as to cover a leading-end upside of the electrode conductor; a metallic chip being composed of a metal making a raw material of nanometer-size particles, and having a leading end that is disposed to face to a leading-end section of the electrode conductor; and a feed device for feeding out the leading end of the metallic chip with respect to the leading-end section of the electrode conductor; the leading end of the electrode conductor having a configuration that is a non-edge configuration; and the electrode conductor, except for the leading end, having an axially-orthogonal cross-sectional area that is larger than an axially-orthogonal cross-sectional area of the metallic chip.