PURPOSE: To fill pure water automatically into a magnet pump and to make easy maintenance when water runs out by providing the magnet pump to the middle of a suction piping between a pure water tank and self-primable pump.

CONSTITUTION: The magnet pump 7 which is a supply pump for pure water is installed to the suction piping 11 between a cleaning pump 8, sampling pump 9, etc., constituted of the self-primable syringe pump and the pure water tank 3. The pure water is automatically filled in the magnet pump as well when the pump 8 is first driven to introduce the water in the tank 3 into the piping 11 at the time of the analysis. The pump 7 is then driven to supply the pure water to a reaction tube cleaning part 12 and a nozzle cleaning part 4. The magnet pump 7 which is advantageous in terms of cost is, therefore, surely usable without using the special pure water tank.