Disclosed is a method for producing nanospheres, by which fine polymer particles that internally contain either a hydrophilic substance and/or a hydrophobic substance and have a particle diameter of nano order can be produced. In the method for producing nanospheres, a solvent in which either a hydrophilic substance and/or a hydrophobic substance is dissolved, a water-immiscible organic solvent in which an amphiphilic polymer is dissolved, and a water-immiscible organic solvent in which a hydrophobic polymer is dissolved are mixed together, then the thus-obtained primary solution is irradiated with an ultrasonic wave, thereby forming a primary emulsion, then an aqueous solvent in which a hydrophilic polymer is dissolved is added into the primary emulsion, thereby forming a secondary solution, and then the secondary solution is irradiated with an ultrasonic wave, thereby forming a secondary emulsion.
