A chemical analyzer supplies a sample and a reagent into a reaction container provided with an opening, mixes a fluid which is to be measured and contains the sample and reagent supplied into the reaction container, measures a property of the fluid in the reaction container, and controls the drive for the mixer. The mixer has a vertical drive machine to move the mixing tool up and down. The control unit controls the vertical drive machine to move the mixing tool up and down in the fluid to be measured in the reaction container so as to cause upward and downward flow of the fluid which is to be measured and is positioned below the mixing tool.