A pigment solution that an organic pigment is dissolved in a solvent, a poor solvent which decreases solubility of the organic pigment in the pigment solution to precipitate particles of the organic pigment, and a dispersant solution containing a dispersant in an organic solvent which acts as a good solvent to the organic pigment are merged in one merging region via each separate inlet flow channel and flowed out from the merging region through one single mixing flow channel, thereby producing particulates by directly dispersing particles precipitated in an aqueous medium comprising the pigment solution and poor solvent into an organic solvent medium containing the dispersant.