An automatic analyzer is disclosed that dispenses a sample and a reagent into each of a plurality of reaction vessels to allow them to react with each other, and that measures the liquid formed as a result of the reaction. This automatic analyzer includes a first reagent storage case for storing the reagent to be used for the reaction, a second reagent storage case for storing the reagent for supplemental purpose, and a reagent conveying unit for conveying the reagent from the second reagent storage case to the first reagent storage case.