An automatic analyzing apparatus can properly determine a quality of an analysis supporting liquid, after being supplied to the automatic analyzing apparatus, which supports an analysis performed in the automatic analyzing apparatus and can properly maintain an accuracy of the analysis. The analysis supporting liquid which supports an analysis of a specimen is dispensed into a reaction vessel by using a specimen dispensing unit which dispenses the specimen, a reagent dispensing unit which dispenses a reagent, a cleaning unit which cleans the reaction vessel, or a diluted solution dispensing unit which dispenses a diluted solution. An optical measurement is performed with respect to a liquid including the dispensed analysis supporting liquid in the reaction vessel. Analysis data of the analysis supporting liquid is generated by using the measured result. The quality of the analysis supporting liquid is determined by comparing the generated analysis data with reference data.