PURPOSE: To remove foreign matter, bubbles in liquid sample without decreasing efficiency of the inspection to cope with a small quantity of the liquid sample and to accurately inspect in a particle sorter using light scattering.

CONSTITUTION: A liquid sample is dispensed to a dyeing tank 12 from a sample cup 11 by a sampling nozzle 4, the sample dyed in the tank 12 is sucked by a sampling nozzle 5, and discharged together with a sheath liquid to a flow cell 25 of a flow cell unit 10. The cell 25 is irradiated with a light, and particles are sorted and counted. Foreign matter in the sample to be discharged from the nozzle 5 is collected by a filter 34, and then discharged with the sheath liquid overflowed from an upper part of the filter 34. Bubbles in the sample liquid are removed from a vent port 31, and the sheath liquid is stored in an aeration tank 21 and then bubbles re removed.