Abstract: To efficiently prevent a decrease in measurement accuracy caused by a change in a test cartridge and an environmental temperature, provided is an automatic analysis device. The automatic analysis device includes: a constant-temperature reservoir (6) to be heated by a heating source (6a) so as to keep a liquid temperature at least in the reaction cell (11c) of the test cartridge (10) in the test stage (KT) at a constant environmental temperature set previously; constant-temperature reservoir control means (7) including a temperature detector (7a), for controlling a set temperature of the heating source (6a) of the constant-temperature reservoir (6) so that the set temperature of the heating source (6a) is higher when the internal environmental temperature is lower than a previously-determined threshold value than when the internal environmental temperature is equal to or higher than the threshold value, based on the internal environmental temperature detected by the temperature detector (7a).