Automatic Analysis Apparatus and Method for Controlling Automatic Analysis Apparatus

[Task] To provide an automatic analysis apparatus including a photomultiplier tube which controls a sensitivity of the photomultiplier tube without adjusting a high voltage value. [Solution] An automatic analysis apparatus according to the present invention includes a photomultiplier tube which detects light from a reaction vessel; a determination unit which determines an output signal of the photomultiplier tube in a case where the photomultiplier tube is irradiated with first light; and a control unit which irradiates the photomultiplier tube with second light to lower a sensitivity of the photomultiplier tube in accordance with a determination result by the determination unit.