1. A quality control method for an analysis supporting liquid in an automatic analyzing apparatus which includes, to perform an analysis on a specimen, a specimen dispensing unit which dispenses the specimen by using, as a pressure transmitting medium, an analysis supporting liquid including purified water and serving to support the analysis on the specimen, a reagent dispensing unit which dispenses a reagent by using the analysis supporting liquid as the pressure transmitting medium, a cleaning unit which cleans, by using the analysis supporting liquid as a cleaning liquid, a reaction vessel in which the specimen and the reagent are mixed and made to react to each other, and a diluted solution dispensing unit which dispenses a diluted solution including the analysis supporting liquid, and which controls a quality of the analysis supporting liquid, the quality control method for the analysis supporting liquid comprising: dispensing the analysis supporting liquid into the reaction vessel by one of the specimen dispensing unit, the reagent dispensing unit, the cleaning unit, and the diluted solution dispensing unit; performing an optical measurement with respect to a liquid, including the analysis supporting liquid dispensed in the dispensing, in the reaction vessel, wherein the optical measurement is performed prior to any reaction using said liquid including said analysis supporting liquid; generating analysis data of the analysis supporting liquid by using a result measured from the optical measurement; and determining whether the quality of the analysis supporting liquid is outside a predetermined range by comparing the analysis data generated in the data generating with reference data, wherein when it is determined that the quality is outside the predetermined range, adjusting a setting of the automatic analyzing apparatus for analyzing the specimen, said adjusting based on a predetermined rule reflective of quality control requirements for the analysis supporting liquid.