A continuous apparatus for the production of nano-particles of organic materials was developed and was applied to leucine. In the new process, a saturated aqueous solutions of leucine continuously flowed over the surface of glycine crystals to dissolve the glycine crystals, and the surface solutions became supersaturated with respect to leucine high enough for leucine to nucleate. Since the nucleated leucine particles were immediately carried away from the surface of the glycine crystal, further growth of the particles was restricted. The continuous production of leucine particles was demonstrated and the mean diameter of produced primary particles was smaller than 200 nm. When the apparent residence time of produced particles was 0.32 s, the particles were not agglomerated and the mean diameter was 70 nm, which was the smallest mean diameter in the present study.