The present invention provides a method for classifying fine particles, the method comprising: introducing a fine particle dispersion in which fine particles are dispersed in a liquid medium into an inlet of a microchannel having the inlet and a recovery portion; and delivering the fine particle dispersion, which has been introduced through the inlet, to the recovery portion in laminar flow, wherein delivering the fine particle dispersion includes classifying the fine particles using the difference in sedimentation speed or floatation speed among the fine particles in the fine particle dispersion. The present invention also provides a device used in the method for classifying fine particles.