Electrolyte analyzers are used in a variety of ways, and problems vary from reagent deterioration due to reagent replenishment, mixing of foreign substances during reagent replenishment, electrode deterioration due to the passage of the validity date, to the operator's inputting errors. It is thus necessary to judge abnormalities of measured values resulting from such inappropriate usage, based on the fluctuation patterns of the results of daily electrolyte calibration. The fluctuation patterns of each measured item are extracted from the results of daily electrolyte calibration. The electromotive force balance ratio between the internal standard solution and high/low-concentration standard solutions is calculated as well as its fluctuation pattern. The obtained fluctuation patterns are compared against atypical fluctuation patterns stored in the electrolyte analyzer. When any of the extracted patterns matches any of the atypical patterns, the analyzer activates an alarm.