An automatic analyzer

Photomultiplier tubes differ between individual products in their performance and deteriorate over time. To use a non-linear calibration curve suitable, it is desirable to strictly reflect changes in signal level. This invention comprises means in order to measure in front of the sensitivity adjustment of a photomultiplier tube by applying high voltages, a same sample under a plurality of high voltage conditions, based on linear relationships between the logarithm of each high-voltage and those of signal levels of an optimal voltage for a measuring process with a predetermined execution sequence in the determining a plurality of measurement operations and to record identification information for identifying each linear relationship, the invention evaluates the functionality level of the photomultiplier tube by evaluating the linear relationship.