PURPOSE: To reduce time and labor in the preparation of a calibration curve by automatically performing the detection of abnormal data and the recalculation of the calibration curve employing an allowable level in addition to the calibration curve calculating operation to permit the operator to accomplish all simply by initially inputting data of a reference sample.

CONSTITUTION: When the operator inputs a measurement starting command into an computation control circuit 2 from a keyboard 3, the circuit 2 stores the results of the measurement of an analyzer 1 into a memory 4. In the preparation of a calibration curve, the operator inputs a known concentration of a reference sample to make the computation control circuit 2 execute a measuring operation and the results of the measurement are stored into the memory 4 while being outputted to a display 5 to plot a graph. The operator determines wether the calibration curve is linear, curve of second or third order observing the graph and inputs the order of the line judged from the keyboard 3 to provide a calibration curve preparation command to the computation control circuit 2. Thus, a calibration curve is determined according to a flow chart defined.