PURPOSE: To obtain a frequency distribution state for every performance grade of a product group directly, by providing a memory means which stores the upper limit and lower limit of the performance of the product in advance, a comparing and judging means, and a counter.

CONSTITUTION: With respect to a relay 1, whih is an object to be measured and whose adjustment is finished, an adjustment sensitivity value X, an open adjustment value Y, and the difference Z therebetween are inputted. Then the total number (n) of the grade number, by which the performance of the products is classified, is individually inputted with respect to the XWZ processing. Then, the lower performance value is loaded from an RAM8 with respect to each grade number (n), and comparison as to whether the measured value is larger than the lower limit or not is performed by a CPU7. When this condition is satisfied, the upper performance limit with respect to the number (n) is loaded from the RAM8, and the comparison as to whether the measured value is smaller than the upper limit or not is compared and judged by the CPU7. When this condition is satisfied, the frequency counter is counted up by 1. If this condition is not satisfied, it is counted down by 1. In this way, the frequency distribution of each grade of the product can be automatically obtained.