A method of manufacturing fine particles of the invention includes introducing a reactive gas flow containing a fine particle source material into a reactor from one side, growing fine particles in a gas phase by heating the fine particle source material in the reactive gas flow, introducing a diluting gas flow into the reactor from another side being almost counter-flow to the reactive gas flow, equalizing flow rates of the reactive gas flow and the diluting gas flow substantially with respect to a cross section of a flow channel, and then stopping growth of the fine particles by merging the reactive gas flow and the diluting gas flow.