PURPOSE: To smoothly execute dispensing of a zero point adjusting liquid and to prevent generation and sticking of air bubbles by providing a water dispensing means for incorporating water in place of a specimen liquid into unused reaction vessels in a reaction vessel array.

CONSTITUTION: The zero point adjusting liquid is dispensed into the reaction vessels after cleaning in an initial setting part. The absorbancies of the respective reaction vessels including the reaction vessels into which the zero point adjusting liquid is dispensed are measured as a measuring means 5 rotates and moves back and forth from the position AWB (broken line arrow). A sample is dispensed from a nozzle 33 into the reaction vessel the use of which is assigned in the dispensing position. A reaction reagent is dispensed from a nozzle 34 into the preceding reaction vessel the use of which is assigned. Pure water is dispensed from the pure water tank 62 into the remaining reaction vessels for which the use is no assigned The zero point adjusting liquid in the reaction vessels in the initial setting part are discharged. The change in the absorbency of the specimen liquids is continuously measured with respect to the many samples by repeating the above-mentioned step.