urfaces of the wells 6 a of the micro-plate assembly 6 (Step S5). [0048] An example of the magnetic particle holding means 4 will now be described with reference to FIGS. 4A to 4C. FIGS. 4A and 4B are a side view and a front view, respectively, of the magnetic particle holding means 4 with the magnets 8 kept away from the micro-plate assembly 6.