A train of cuvettes are held on a turntable and serum specimen is sequentially sampled each time the turntable makes a revolution through more than 360.degree.. While the turntable is at rest, blank solution is poured into one cuvette, reagent is put into another cuvette and reactant solution is drawn out of still another cuvette in specified positions respectively in the path along which the train of cuvettes are conveyed. During a single rotational operation of the turntable, these cuvettes sequentially transverses the light path in the photometer so that the light absorbances for the respective cuvettes are measured. Both the absorbances for cuvettes containing reactant solutions for different samples and the absorbance for a cuvette containing only the blank solution are measured by a single photometer. The difference between the value of measurement obtained from a specified cuvette filled with reactant solution and the value of measurement obtained from the same cuvette filled with blank solution alone, is calculated and an analyzed value corrected is obtained for any desired analysis item in accordance with the calculated difference.