The present invention provides fine drug particles with submicron sizes excellent in long-term dispersibility. Specifically, it provides a method for producing ultrafine drug particles having an average particle size of 10 nm to 1000 nm, by 1) dissolving a drug in a good solvent or a mixture of good solvents to prepare a drug-containing solution; 2) mixing the drug-containing solution with a solvent being a poor solvent or a mixture of poor solvents for the drug and being miscible with the drug-containing solution in the good solvent or a mixture of good solvents; and 3) subjecting the prepared mixture directly to emulsification under a set processing pressure using a high-pressure homogenizer without carrying out a pretreatment step for adjusting the drug to have an average particle size of 100 μm or less, and an apparatus for producing the particles.