An automatic analyzer detects measurement value abnormalities stemming from reaction process anomalies caused by the presence of foreign matter or bubbles. It is determined whether the results of concentration calculation based on light quantity data from multiple target detectors each fall within an applicable determination range. If the results fall within the determination range, an average value of the results of concentration calculation with the target detectors is calculated, and if not, an out-of-determination-range flag is given. A default fluctuation range is retrieved regarding the average value of the results of concentration calculation. The fluctuation range of the results of concentration calculation with the multiple target detectors is calculated. If the fluctuation range is found to fall within the default range, the results of concentration calculation are output to a display; and if outside the default range, a reexamination request is displayed with an added measurement value abnormality alarm.