A manufacturing method for nanoparticles including an amphiphilic block polymer having a uniform particle diameters has steps of forming a laminar flow of polymer solution by inducing a solution comprising an amphiphilic block polymer having a hydrophilic block and a hydrophobic block in an organic solvent into a polymer solution supply flow passage, a step of forming at least two laminar flows of a water system solution by inducing the water system solution to at least two water system solution supply passages, and a step of forming nanoparticles comprising the amphiphilic block polymer by making a confluence as if at least two laminar flows of water system solution sandwich the laminar flow of the polymer solution.
