The issue of the present invention is to provide a kind of method crystalline drug nanoparticle to which nanoparticle includes that crystalline drug can easily continuous production be without drying steps and organic solvent and a kind of nano particle method, thus crystalline drug can be nano particle. The mode drug of the content of crystalline pharmaceutical and polymer reaches the total amount of 15-40 mass % relative to drug and water-soluble polymer. Then by heated at a temperature of gained mixture at least 50 °C lower than drug melting point and mediate. OrDrug mixes, and reaches the total amount of 20-40 mass % relative to drug and water-soluble polymer with the mode drug of water-soluble polymer content. Then the drug and kneading that at least 10 °C are higher than fusing point will be heated at a temperature of gained mixture.
