PURPOSE: To make it possible to enhance the stabilization and reproducibility of batchwise collection, by constantly keeping the height of the level of the liquid containing no particles present in a container for accumulating a liquid containing particles to supply the same to a small chamber.

CONSTITUTION: A small container 1, a large container 12 and piping 13 are provided. The pressure of a gaseous phase applied to the surface of the liquid in the small container 11 is balanced with the total pressure of the pressure of the gaseous phase 16 above the surface of the liquid in the large container 16 and the liquid head pressure difference of the liquid in the large container 12 having in relation to the surface of the liquid in the small container 11. When the liquid 17 in the small container 11 is flowed in the small chamber 1 and the liquid level thereof is lowered, the gaseous phase 15 is introduced into the large container 12 through the piping 13 and, contrarily, the liquid 18 in the large container 12 is flowed in the small container 11 through the piping 13. When the liquid level in the small container 11 reaches a height for perfectly closing the opening part of the piping 13, the gaseous phase 15 can not move to the large container 12. By this method, the liquid in the small container 11 is continuously flowed to the small chamber 1 but the height of the liquid level in the small container 11 is kept constant until the liquid in the large container 12 can be perfectly consumed.