PURPOSE: To facilitate analytic operation by making it possible to select an optical filter for a desired component automatically through setting an analysis-component selection switch to the position that corresponds to the desired component.

CONSTITUTION: When analysis-component selection switch 13 is changed over corresponding to the analysis component of sample solution 7' in measurement cell 7, rotary-disk optical filter holder 5 coupling with driving motor 11 via optical-filter automatic selecting circuit 12 rotates automatically. This rotation permits selected optical filter 6 to arrive at a constant position on the optical path. At this time, filter 6 is detected with combinations of position detection holes 14 and 15 and photocouplers 9 and 10, so that it is automatically stopped via optical-filter automatic selecting circuit 12.