There is provided an automatic analyzer for detecting measurement value abnormalities stemming from reaction process anomalies caused by the presence of foreign matter or bubbles without recourse to complicated processing or functionality of the analyzer. Checks for measurement value abnormalities are started to determine whether the results of concentration calculation based on light quantity data from multiple target detectors each fall within an applicable determination range (steps a, b). If the results of concentration calculation are found to fall within the determination range, an average value of the results of concentration calculation with the target detectors is calculated. If the results of concentration calculation are found to fall outside the determination range, an out-of-determination-range flag is given, and an average value of the results of concentration calculation with the target detectors is calculated (steps c, d). 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. It is then determined whether the calculated fluctuation range falls within the default range (steps e, f, g). If the fluctuation range is found to fall within the default range, the results of concentration calculation are output to a display unit; if the fluctuation range is found to fall outside the default range, the display unit is caused to display a reexamination request and add a measurement value abnormality alarm (steps h, i, j).