PURPOSE: To take a high-precision, stable measurement by calculating a distribution center value from numbers of resistance measured values, referring to a specific table and setting resistance values of plural ranks, and performing rank classification on the basis of a mean resistance value obtained by measuring one resistance by many times.

CONSTITUTION: Tens of fixed resistances are measured at random and the distribution center value is calculated automatically by a computer, etc., while up to the 3rdWthe 5th data from the largest and the smallest values are ignored. The effective resistance value data table is referred to on the basis of the distribution center value to set the resistance values of the upper and lower same numbers of ranks similarly and automatically. Then, the resistance value of one resistor is measured by (n) times to calculate their mean value, and the rank of the set resistance value is referred to classify a resistance group within a set rank. The high-precision and stable resistance value measurement is performed speedily by the classification based upon this accurate distribution center value without the need for resetting, reclassification, etc., due to deviation in distribution center value.