To provide an autoanalyzer capable of simply preventing the evaporation of a held liquid even if a container is small-sized.

The autoanalyzer 1 for measuring the optical characteristics of the liquid is provided with a container C for holding the liquid and an evaporation preventing liquid dispensing device 13 for dispensing an evaporation preventing liquid, which cuts off the liquid held in the container from the open air to prevent the evaporation thereof, on the liquid held in the container before the optical characteristics of the liquid are measured. Further, the autoanalyzer 1 has a specimen dispensing mechanism 3 for dispensing a specimen to the container and reagent dispensing mechanisms 5 and 6 for dispensing reagents to the container. Furthermore, the autoanalyzer 1 has stirrers 11 and 12 for stirring the specimen and the reagents and the evaporation preventing liquid dispensing device is constituted so as to dispense the evaporation preventing liquid on the reaction liquid after the specimen and the reagents are stirred by the stirrers but before the optical characteristics of the reaction liquid are measured.