An object is to provide an automatic analyzer that prevents an effect of various environmental changes on an equilibrium state of an immunological binding reaction. An automatic analyzer of an embodiment of the invention includes a B/F separation unit that executes a B/F separation step separating an unreacted component and a reacted component from a liquid in which a sample and a reagent are reacted, a detection unit that detects a reacted component in the liquid after the B/F separation step, and a temperature maintaining unit that maintains the B/F separation unit and the detection unit in substantially the same temperature environment.