When the automatic analyzer is installed in an environment with a high altitude and different external atmospheric pressures, there is a problem that an amount of vacuum suction decreases due to a decrease in suction performance of a vacuum pump and it is difficult to perform vacuum suction of an analyzed reaction liquid. In view of the above, by newly providing a pressure adjustment mechanism within a flow path connecting a vacuum tank to vacuum pump, it possible to control the pressure difference between a pressure in the vacuum tank and an external atmospheric pressure where the analyzer is installed to be constant regardless of the installation environment. Additionally, by providing a hole in communication with the outside in the vacuum tank or a vacuum bin, it possible to control the pressure difference between the pressure in the vacuum tank and the external atmospheric pressure where the analyzer is installed to be constant regardless of the installation environment.