To provide a fine particle classifier classifying particles of a specific particle size with high through-put.

The fine particle classifier classifying charged particles in aerosol gas is provided with: two facing electrodes; a gas supply means causing sheath gas to flow between the electrodes; an electric field forming means forming an electric field between the electrodes; an inlet slit provided at one electrode; a particle charge means charging aerosol gas into the sheath gas from the inlet slit; and an outlet slit provided at the other electrode, wherein the outlet slit is covered with a conductive member having a plurality of holes. This configuration allows the fine particle classifier to perform theoretical classification since the electric field between the electrodes is uniformized by the presence of the conductive member, even if an opening width of the outlet slit is widened for performing high through-put classification. The conductive member is preferably composed to have a plurality of mesh-like or slit-like holes.