PURPOSE: To prepare a large amount of particles having a uniform particle size in good yield by allowing liquid droplets to fall into a coagulating solution having air bubbles formed therein by the diffusion of air.

CONSTITUTION: Pressure gas is introduced into a raw solution tank 1 from a pressure gas introducing pipe 10 and a raw solution A is extruded from a supply pipe 11 to be supplied into a vibrator 2. The raw solution A in the vibrator 2 is vibrated by a vibrator 3a vibrated on the basis of the frequency due to the definite frequency signal from a transmitter 4 through a vibration plate 3b and emitted as a liquid stream from a falling orifice 5. The emitted liquid stream is disrupted during falling by the vibration propagated through the liquid stream and formed into a globular shape by the surface tension of the solution to fall. Since the particle size of liquid droplets B is determined by the diameter of the orifice 5, emitting flow velocity and vibration frequency, these conditions are appropriately set to form the liquid droplets B having an arbitrary particle size. The liquid droplets B fall on the surface of the coagulating solution D in a coagulating solution tank 6 but receives the buffer action due to a large number of the fine air bubbles introduced from an air diffuser and the falling shock of the liquid droplets is relaxed and the dispersion or flattening thereof is prevented.