PURPOSE: To always perform a measurement under the same condition with washing of the precedent sample, by connecting both ends of the tube linking to the sample chamber with piercing through the chamber to the fixed tanks and controlling the electromagnetic valve in accordance with the liquid level.

CONSTITUTION: When the sucking pressure is applied to the insulated repeating part 18 after opening the electromagnetic valves 8 and 23, the preceding sample of the sample chamber 1 is sucked to the part 18 from one end of the tube 4 linking to the chamber piercing through the chamber 1 via the detector pellet 7. As a result, the liquid level lowers at the supply part 10 of the tube 4 connecting to the liquid sink part 11, and thus the electromagnetic valve 15 opens via the liquid level detector 14. Then the cleansing solution is supplied from the tank 13 to carry out the exhaustion of the precedent sample of the chamber 1 as well as the necessary washing. When the washing is over, the flow-in of the sample is controlled to the chamber 1 by the control of the electromagnetic valve via the liquid level detecting means 16 and 17, etc. Thus the precedent sample is washed with every measurement via the electrodes 24 and 25, etc. As a result, the particles of the erythrocyte, the leucocyte and the like can be detected and measured accurately under the same condition.